128 KANSAS ACADEMY OF SCIENCE. 



"The chin is retreating in the quadrumana, . . . and a retreating chin in 

 man is a marked monkey character" (Cope. op. cit.)\ that is, a chin that is retreat- 

 ing from the alveolar border backward, as a normal condition, and not as a result 

 of the accidental lack of development of the lower jaw, or a lingering embryonic 

 form. The lower jaw is somewhat inconstant, and may be very small or very large 

 as compared with the rest of the face, leading to malposition and irregularity of the 

 teeth, as frequently observed by dentists, and the complete alteration of the expres- 

 sion of the mouth. But the chin, as a distinct feature, is independent of the form of 

 the jaw, and occurs as a part developed upon and added to it — the part known as 

 the bony symphysis of the lower jaw. It is a powerful and expressive feature in 

 man. and serves much to give character and impressiveness to the face. A bold: 

 strong chin gives strength to a face, and a weak, retreating chin weakens a face as 

 much as a weak, embryonic nose. 



The chin is a distinctively human feature. Mivart ("Man and Apes") says: "A 

 striking feature of the human skull is the prominence of the inferior margin of the 

 lower jaw in front, i. e., the presence of the chin. The feature is quite wanting in 

 the gorilla, orang, and chimpanzee" — in fact, in all the quadrumana, except a slight 

 approach to it in the siamang. This is easily observed by comparisons of the skulls 

 of monkeys and man. Even the lower races of man have, as a rule, retreating chins, 

 especially when there is prognathism present, and, like that, it is a quadrumanous 

 feature. 



The descent of the movements of expression is an interesting part of our subject 

 and opens a wide field, the study of which may enable us to find the origin and trace 

 the descent of many of the expressive movements of the face of man. We notice 

 first that many animals express emotions by the motions and movements of parts 

 which with man have become obsolete or were never used by his ancestors. Thus, 

 the horse expresses his feelings — anger, fear, etc. — most plainly with his ears; the 

 expressive organ of the dog is the tail; the cat expresses her feelings by the arching 

 of the back and the movements of the tail and ears, and the standing hairs are ex- 

 pressive in both cat and dog. There are other expressive movements that lie out- 

 side of the facial features, but with these we will have nothing to do at present. The 

 eyes are expressive in all animals, and in that they much resemble man. 



Facial expressions, the movements of the face, were undoubtedly developed with 

 the growth of the mind, as new emotions and mental faculties were called into ex- 

 istence which demanded expression. The first expression of the feelings or of the 

 ideas was sign language, and facial expression remains with man as a rudiment of 

 that means of communication, before the origin and development of language, for 

 sign language is used even by animals, in expressive movements of different parts of 

 the body, which are well understood. 



Charles Darwin says ("Expression of the Emotions in Man and Animals") that 

 he "attended as closely as possible to the expression of the several passions of ani- 

 mals, as affording the safest basis for generalizations on the causes or origin of the 

 various movements of expression. ... It seems probable that the habit of ex- 

 pressing our feelings by certain movements, though now rendered innate, had been 

 in some manner gradually acquired." Again he says ("Descent of Man"): "The 

 relative position of our features (as compared with the quadrumana) is manifestly 

 the same, and the various emotions are displayed by nearly similar movements of 

 the muscles and skin, chiefly above the eyebrows and around the mouth. Some few 

 expressions are, indeed, almost the same, as in the weeping of certain kinds of 

 monkeys and in the laughing noise made by others, during which the corners of the 

 mouth are drawn backward and the lower eyelids wrinkled. The external ears are 

 curiously alike. In man the nose is much more prominent than in most monkeys; 



