In this study the authors used ultrasound to demonstrate characteristic internal actions of the tongue during suckling. Its medial portion, into which the genioglossus is inserted, moves in relation to its lateral portions, into which the styloglossus and hyoglossus are inserted. A peristaltic wave of successive inferior and superior displacements moves posteriorly in the medial portion, compressing or 'milking' the nipple and propelling the expressed milk towards the pharynx. The lateral portions of the tongue enclose the nipple and the bolus and serve as reference for the displacements of the medial portion. These observations are related to anatomical studies of the tongue. The coordination pattern of suckle is compared with that of pharyngeal swallow. In instances where suckle and swallow are immediately sequential, the peristalsis which is common to both is continuous in the oral and pharyngeal portions of the food pathway.