The teeth and teeth of mammals are fixed in the gag because they have to bite the prey and chew food. There is an exception. The scientists at the University of Pretoria, Andrew McKenzie and Arno Weber, say that the splinters of the impalas are mounted on a kind of cylinder, which can move two millimeters backwards and forwards. This facilitates the elimination of hogs and other parasites that are found between hairs. It can be said that they have a narrow comb in the mouth.