DEVELOPMENT OF THE AURICLE IN THE HUMAN EMBRYO. 119 



Schmidt (1902) made a comparative anatomical study of the auricle, with 

 examples from the following orders: Primates, Prosimiae, Rodentia, Perissodactyla, 

 Artiodactyla, and Carnivora. The paper is accompanied by a limited number of 

 excellent drawings. The author regards the human auricle as rudimentary and 

 finds that most of its morphological characteristics can be recognized in the ear 

 of other mammals. 



Baum and Dobers (1905) describe the development of the auricle in the pig 

 and sheep. In the early pig embryo six auricular hillocks are found, corresponding 

 closely to the His description for man. Hillock 1 can not be recognized in the sheep ; 

 in the pig it becomes the tragus. The ear-fold is derived from hillocks 4, 5, and 6. 

 Hillocks 2 and 3 acquire cartilage and form the cms and helix ascendens. Hillocks 

 4, 5, and 6, in addition to forming the ear-fold, become elongated into three longi- 

 tudinal ridges which constitute the anthelix. Hillocks 2 and 5 fuse and create a 

 transverse ridge which divides the fossa angularis into a dorsal part (scapha) and a 

 ventral part (concha), which is continuous with the external auditory meatus. 

 This paper is accompanied by very few figures of the earlier stages, so that it is not 

 possible to follow accurately the transitions referred to by the authors. They 

 describe the development of the scutulum and find that it has the same origin as 

 the auricular cartilage and is a derivative of it. They regard it as identical with 

 the spina helicis of man, which has become detached by the pull of the massive 

 anterior auricular cartilage. 



Keith (1906) gives the results of an anthropological study of the mature auricle, 

 with the view of determining the relation of one group of people to another, his 

 records extending to 8,567 males and 6,577 females, belonging to Germany, Scotland, 

 England, Wales, and Ireland, and including representatives of the insane, criminal, 

 and vagrant classes. He regards it as unlikely that we shall obtain any light on 

 racial affinities from the studj^ of the form of the auricle. 



Henneberg (1908) describes the development of the auricle in the rat, rabbit, 

 and pig. His descriptions are accompanied by a series of excellent illustrations, 

 which give the principal stages of development from the time of the formation of 

 the auricular hillocks until the auricle has acquired its mature characteristics. 

 The fate of the individual hillocks appears to be the same in the three forms studied. 

 Henneberg differs from Schwalbe chiefly in regard to hillocks 4 and 5, which, 

 according to him, give origin directly to the ear-fold (primitive scapha). By the 

 fusion of hillocks 1 and 6 the first gill-cleft becomes converted into the fossa angu- 

 laris. Through the undermining of the surrounding wall this fossa becomes con- 

 verted into the concha, while the wall itself gives origin to the tragus, antitragus, 

 helix, and parts of the definitive scapha. In all of the three animals studied, the 

 inner surface of the scapha shows the presence of longitudinal ridges which are 

 derived from the hyoidal hillocks. In the rodents these disappear, but in the pig 

 they remain as the permanent longitudinal folds. 



In 1910 Henneberg made a study of the function of the auricle, in which special 

 attention is given to the closure mechanism as it occurs in a variety of mammals. 

 He believes that in man the auricle serves not only as a sound collector but also 



