i yo THE HEAD AND NECK 



The parathyreoid glands are derived from the entoderm 

 lining the third and fourth visceral pouches (p. 149). 



Thyreo-glossal Cysts or tumours may arise in the lingual 

 or cervical part of the duct. In the former case they lie between 

 the genio-glossi (p. 148) ; in the latter they are median, and 

 lie superficial to the thyreoid or cricoid cartilage. Recurrence 

 of the condition is certain if any procedure short of complete 

 excision is attempted. The operation may be one of great diffi- 

 culty, as it frequently entails a dissection right up to the foramen 

 caecum. The procedure is similar to that already described for 

 the removal of a branchial fistula, but it is advisable to resect 

 the central portion of the hyoid bone lest some of the germinal 

 cells of the tract are embedded in it (p. 169). Recurrence of 

 the condition due to neglect of this important detail is now a 

 well-recognised possibility (Stiles). 



THE FACE, MOUTH AND PHARYNX 



Bony Landmarks. At the junction of the intermediate 

 and medial thirds of the upper margin of the orbit the supra- 

 orbital notch can be examined, and the supra-orbital nerve, 

 which it transmits, can be rolled against the bone. The super- 

 ciliary arch (ridge) lies just above the upper margin of the orbit 

 and is more prominent medially. In the middle line the two 

 arches are united by an elevation, the glabella ; it lies a little 

 above the nasion, a depression at the root of the nose, which 

 indicates the naso-frontal suture. If the nasal bones are traced 

 downwards in the median line, their union with the nasal car- 

 tilages will be recognised by a slight depression, and on each 

 side of the nose at this level the margins of the apertura piri- 

 formis (osseous anterior nares) can be felt. The anterior nasal 

 spine is recognised by placing the finger on the middle of the 

 upper lip and pressing upwards against the nasal septum. 



The zygomatic process of the temporal bone runs forwards 

 from the tragus to articulate with the zygomatic (malar) bone, 

 forming the zygomatic arch. Below the anterior part of the arch 

 the fingers can be inserted into the infra-temporal (zygomatic) 

 fossa, but the temporal fascia, which is attached to the upper 

 border of the arch, is so dense that the temporal fossa cannot be 

 explored in the same way. The tubercle of the zygomatic 

 (malar) bone is felt when the upper border of the arch is traced 



