Abstract
Sucking movements of a nine-month female infant were studied using a highpersensitive X-ray TV system. During the movements, the epiglottis and soft palate showed no contact, but the airway from the nasal cavity was kept open. In the sucking motion, the tongue moves like a rolling wave form moving dorsally and ventrally. The depth of the trough at the middle portion of the rolling tongue was 5.6 mm and rather larger than the jaw movement. The hyoid bone is fixed in forward and upward, while the function of the suprahyoid-muscles to open the jaw may not act easily and the jaw may loose mobility. Concerning the compression of the nipple, although the neck of the nipple was compressed during the closing phase of the jaw, on the whole, the nipple was confirmed to be compressed tonically while the front portion of the tongue moved ventrally. This compression would act as the function of milking from the nipple, and stabilizing the front portion of the tongue to make depressing the middle portion of it easy. The oral cavity was closed at the front with the tongue and lips and at the rear with the base of the tongue and soft palate to form a closed cavity. Large alterations in the sucking pressure may be generated by the rolling wave of the tongue which moved rapidly in the small cavity of the infant. It is suggested that the depression of the middle of the tongue may be supported by both the stabilization of the jaw and the compressive movement of the tongue tip.
