Vol. IX] VON G ELD ERN— FLORIDA CHAMELEON 317 



III 



The basi-hyal lies in the midline just caudad to the larynx 

 and base of the tongue, being intersected by a line running 

 through the eyes. It is covered by skin, superficial fascia and 

 the thin, superficial mylohyoid. (Fig. 2.) 



The processus entoglossus lies deeply embedded between 

 the extrinsic muscles of the tongue and terminates near the 

 symphysis of the jaw. (Figs. 2, 3, 4.) 



The anterior horn lies beneath the suprahyoid and hyoglos- 

 sus muscles, crosses the pterygoid muscle, thence curving 

 around the mandible and ending in a mass of connective 

 tissue just caudal to the ear. (Fig. 2.) 



The posterior horn is more superficial, being covered in 

 part by the thin mylo-hyoid only. Distally it curves over the 

 side of the neck just caudad to the mandible, ending in the 

 superficial connective tissue. (Figs. 2 and 3.) 



The processus retrobasalis is superficial, being embedded 

 in loose connective tissue just beneath the skin. It lies in 

 the midline and extends to the chest wall. (Figs. 2 and 3.) 



The hyoid apparatus forms a typical lever of the first class. 

 The fulcrum is at the junction of the basi-hyal and the pos- 

 terior horn. The short arm of the lever, which is the power 

 arm, is the first part of the anterior horn. The processus 

 retrobasalis forms the long arm. (Fig. 1 A.) 



A force exerted from the extremity of the anterior horn or 

 short arm in a caudal direction, will, due to a slight dorsal 

 inclination of the latter, cause it to swing dorsad and caudad, 

 thus rotating the body at the fulcrum and swinging the hori- 

 zontal processus retrobasalis through an arc of 90° in a 

 cephalad and ventrad direction, to assume a vertical position. 

 Necessarily the force must be equally applied to the first part 

 of both horns. The second part of the anterior horns and the 

 posterior horns act as supports and tend to prevent any 

 lateral displacement of the long arm of the lever during its 

 assumption of the vertical position. 



Necessarily the processus entoglossus would, on meeting the 

 resistance of the tongue during the rotation of the body, be 

 bent dorsally, but its extreme flexibility renders this possible. 



