Vol. IX] VON GELDERN— FLORIDA CHAMELEON 321 



hyoid. It tends to pull the anterior horn cephalad after the 

 latter has been pulled caudad by the cerato-hyoid. (Fig. 5.) 



The cerato-hyoid takes its origin from the medial two-thirds 

 of the second part of the anterior horn. Its fibres run almost 

 directly caudad and insert along the posterior horn, except 

 for about one-sixth of the proximal and distal ends. This 

 muscle pulls the first part of the anterior horn caudad and 

 dorsad, thus rotating the body at the fulcrum and swinging 

 the processus retrobasalis cephalad and ventrad. (Fig. 4.) 



The hyoglossus takes its origin along the posterior horn ex- 

 cept for one-sixth of the distal end. The fibres converge and 

 form a rounded belly which inserts along the inferior surface 

 of the tongue by attachments to the intrinsic- muscles. This 

 muscle pulls the tongue backwards. 



The mylo-glossus has a common origin with the mandibulo- 

 hyoid along the inner aspect of the anterior two thirds of the 

 mandible. It inserts along the side of the tongue. Its fibres 

 run medio-caudad so that besides pulling the tongue from side 

 to side when acting independently, it may be protruded when 

 it acts with the one on the opposite side. (Fig. 4.) 



V 



In the distension of the throat fan the elastic skin of the 

 throat is raised by the raising of the processus retrobasalis 

 from the horizontal to the vertical position. The thinness of 

 the distended fan is due to the cohesive quality of the two 

 moist, 6pposing surfaces of skin, as well as atmospheric 

 pressure. Its semi-circular outline is due to the tapering 

 cartilages which, near their proximal end, are able to resist 

 the elasticity of the skin but are unable to do so at their distal 

 part, owing to increased flexibility. 



The assumption of the vertical position by the processus 

 retrobasalis from the horizontal, is due to the contraction of 

 the cerato-hyoids which pulls the first parts of the anterior 

 horns dorsad and caudad and causes the seconds parts of the 

 anterior horns to slide caudad and laterad. At the same time, 

 the basi-hyal is raised by the pull of the sterno-hyoids on the 

 posterior horns. The entire apparatus is steadied by the an- 

 tagonistic action of the mandibulo-hyoids and genio-hyoids 



