There is no generally agreed definition of the human and subhuman face. For primatologists the definition forwarded by PERKNOPF (1957) is most agreeable: all structures of the head which can be seen from en face belong to the human face. The face is a combination of structures heterogeneous in both anatomy and function (forehead, eyes, mouth, pelage, etc.). They are different in qualities (e.g., color of the skin or the hair) and quantities as well (length of the jaw or the hairs of the mane). Despite the heterogeneity in form and function, the face as a whole appears as a unit, because in facial expressions there is always more than one structure involved. Blage, etc.). They are different in qualities (e.g., color of the skin or the hair) and quantities as well (length of the jaw or the hairs of the mane). Despite the heterogeneity in form and function, the face as a whole appears as a unit, because in facial expressions there is always more than one structure involved. Blage, etc.). They are different in qualities (e.g., color of the skin or the hair) and quantities as well (length of the jaw or the hairs of the mane). Despite the heterogeneity in form and function, the face as a whole appears as a unit, because in facial expressions there is always more than one structure involved. Because of the frontally oriented eyes and the stereoscopic vision, the facial structures are situated on the head so that they can be seen from in front. This is the reason why primate display mainly face to face. The concepts of the internal and external face are justified only in terms of topographical anatomy.