ORGAN OF HEARING IN MAMMALIA. 



245 



are met with in the dissection of Europeans. The attollens 

 auriculae ' is the largest, fig. 190, #, arising from the epicranial 

 aponeurosis ; its fibres converge to be inserted in the surface of 

 the ear-cartilage next the head. The ( retrahens auriculae,' ib. 

 c, d, consists of two or three fascicles arising from the mastoid 

 and inserted into the back of the conch. The f attrahens auriculae,' 

 ib. b, arises from the zygoma, and is inserted by a broad but 

 short tendon into the helix near the tragus. Five groups of 

 fibres have been made out in the auricle itself, and are described 

 as the ( intrinsic muscles.' The 'helicalis major,' fig. 191, ; 

 the ' helicalis minor,' ib. c\ the t tragicus,' ib. d\ the antitragicus, ' 

 ib. e, and the t transversalis auriculae,' fig. 192, a. 



All these muscles of the human external ear exemplify the 

 Lamarckian law of degeneration from disuse, In the primitive 



191 



192 



a 



Front view of auricular cartilage, and intrinsic 

 muscles, xcviu". 



Back view of auricular cartilage and 

 transversalis muscle, xcvin". 



men of the ( stone-period,' they probably existed in normal size 

 and force. 



In thus concluding the comparative anatomy of the organ of 

 hearing, it has to be owned that, hitherto, the experiments of the 

 accomplished and ingenious physicists and physiologists to that 

 end have failed to demonstrate the relations of the various 

 exquisite structures to sound, in the satisfactory way in which 

 those of the eye are understood to relate tt> light. The vesti- 

 bular part of the labyrinth may be inferred to detect the presence 

 and intensity of sound, especially as conveyed through the 

 external ear and tympanum. It has been conjectured and argued 

 that the semicircular canals are concerned in forming a judg- 

 ment of the direction of sounds. The cochlea receives those 

 sounds which are propagated through the bones of the head, and 

 is conjectured to be the medium of the perception of the pitch of 

 notes, and of the timbre or quality of sounds. The tympanum 



