The mechanism of vocalization in the marsupial Didelphis azarae

A study of provoked animals in vivo, of dissection of adult animals and of serial sections of 6 foetuses suggested that the mechanism of drawing the normally intra-nasally situated larynx into the mouth in vocalization is as follows: the joint contraction of the genioglossus, mylohyoid and geniohyoid muscles is suggested as the agent which induces the forward movement of the hyoid. The sternohyoid and sternothyroid, contracting simultaneously with the palato-pharyngeus muscle, could assure the return of the larynx to its original position inside the nasal cavity. A well-developed thyrohyoid muscle would be responsible for the displacement of the larynx as a result of the forces exerted on the hyoid.