With regard to the mechanism of an infant's suction, many problems still remain unsolved. According to the studies by Burdach,1 Funke,1 Meissner,2 Allix3 and Herz,4 the negative pressure in an infant's oral cavity which is necessary for sucking milk is chiefly made by inspiratory action, while Biedert5 and Vierordt6 attribute it to the enlargement of the vertical diameter of the oral cavity, the lower jawbone being drawn downward. After detailed researches, Auerbach7 in 1888 made a new discovery in connection with the physiology of suction in general. He divided the action into two kinds: (1) suction by inspiration, and (2) suction by the mouth, or the tongue.
Suction by inspiration is made by adults, and the negative pressure in the mouth necessary for suction is chiefly caused by inspiratory action; while suction by the mouth is made by infants, and the negative