Hyo-mandibular relationships during feeding in the cat.

The movement of the hyoid was studied by cineradiography to obtain information on the movements of the tongue base. During feeding on solid foods, the path of movement of the hyoid in the sagittal plane was highly variable and often complex when referred to the palate. When the effect of jaw movement was excluded by referring hyoid movement to the line of the moving mandible, the path of movement of the hyoid became simpler and less variable, tending to an ellipse. The reversal of hyoid movement from backwards to forwards (relative to the mandible) occurred close to the time at which minimum gape was reached and the reversal from forwards to backwards occurred either (a) at low angles of gape during early jaw opening or (b) at maximum gape. Two different categories of stable state therefore existed together with some intermediate forms of relationship in which the periodicity of jaw movement and of hyoid movement differed. Although the mechanical linkage between jaw and hyoid was a major influence on hyoid movement related to the palate, it was not the sole source of variation in the pattern of that movement.