THE ANTERIOR PART OF THE NECK 121 



median line and locate in sequence the body of the hyoid 

 bone, the angular anterior border of the thyreoid cartilage, 

 the rounded arch of the cricoid cartilage and the rings of the 

 trachea. The latter are partly masked by the isthmus of the 

 thyreoid gland. Place the thumb and the forefinger on the 

 body of the hyoid bone and carry them backwards, one on 

 each side, along its greater cornua. Note that the posterior 

 ends of the cornua lie immediately in front of the anterior 

 borders of the sterno-mastoid muscles. Above the body of 

 the hyoid bone lies the submental triangle bounded superiorly 

 by the mylo-hyoid muscles, which form the diaphragm of the 

 mouth ; and above each greater cornu is the corresponding 

 sub maxillary region. Between the body of the hyoid bone 

 and the upper margin of the thyreoid cartilage is the thyreo- 

 hyoid space, bounded posteriorly by the middle part of the 

 thyreo-hyoid membrane, which lies anterior to the upper part 

 of the pharynx and the middle of the epiglottis (Fig. no). 

 Trace the upper border of the thyreoid cartilage backwards 

 and note that it terminates, on each side, in a pointed projec- 

 tion, the superior cornu, which lies immediately in front of 

 the anterior border of the sterno-mastoid. Between the lower 

 margin of the thyreoid cartilage and the upper border of the 

 cricoid cartilage lies the cricothyreoid ligament, forming part 

 of the anterior wall of the lower portion of the larynx. 



The dissectors should make themselves thoroughly familiar 

 with the landmarks mentioned above, both on their own necks 

 and on the necks of their friends, and they should note that, 

 whilst in the dead subject there may be some difficulty in 

 palpating the isthmus of the thyreoid gland, as it crosses 

 anterior to the second, third and fourth rings of the trachea, 

 they will have no difficulty in locating the small soft cushion- 

 like mass in the living subject. 



Dissection. The skin was cut along the lower border of the 

 mandible at the commencement of the dissection of the face ; 

 now, make a median incision through it, from the chin to the 

 sternum, and turn the triangular flap, thus marked out, back- 

 wards and laterally, to a short distance beyond the anterior 

 margin of the sterno-mastoid. When that is done the super- 

 ficial fascia covering the anterior triangle on each side will be 

 exposed ; it is thickest and most laden with fat in the submental 

 region. In the upper and posterior part of it lie the fibres of the 

 platysma, running upwards and forwards towards the mandible. 

 Some of the anterior fibres of the muscle gain attachment to the 

 anterior part of the lower border of the mandible, and some 



