234 



COMPARATIVE ANATOMY 



auditory ineatus. These auricular eminences unite to form a nearly con- 

 tinuous ring, on which are later formed the characteristic protuberances 

 known as the helix, antihelix, tragus, and antitragus. The variations in the 

 form of the pinna which are seen in various Mammals concern essentially the 

 later formed portion which projects upwards and backwards from the head 

 (Fig. 188). 



FIG. 88. THE PIXNA OF VARIOUS PRIMATES. 



In A, the shaded portion (b) represents the zone of the auditory eminences of the- 

 embryo, the unshaded that of the later formed auditory fold. B, Man, 

 Baboon and Ox, drawn to the same scale and superposed : s', s," s, spina or 

 tip of the ear. C, Macacus rhesus, with upwardly directed tip ; and D, Cerco- 

 pithecus, with backwardly directed tip. E, Man : the muscles are indicated 

 as follows m.a, attolens auriculae ; m.a', antitragicus ; m.t, tragicus ;, 

 m.f, inconstant muscle, extending from the tragicus to the margin of the 

 helix ; m.h', helicis major ; m. h" helicis minor ; s, tip of the ear rolled over. 



A -D, after Schwalbe ; E after Henle. 



