Movements of the Lower Jaw of Cattle during Mastication

Abstract

AMONG the biological phenomena exhibiting a definite sense of rotation, as, for example, the growth certain creepers and of the shells of snails, one that does not seem to have been studied and to which we wish to direct attention here, is the masticating motion cattle. Close investigation shows that the lower jaw of the animal is displaced with respect to the upper jaw, not in a purely horizontal or a purely vertical direction, but simultaneously in both directions with such a phase difference that a clearly evident rotation results. Theoretically this can, of course, take place in two senses, and observation teaches that both possibilities are realised in Nature. Taking the direction of the food as positive, we shall denote as right- and left-circular cows those of which the chewing motion, viewed from the front, turns clockwise and counterclockwise respectively.