CHAPTER XXX 

 THE SENSE OF HEARING 



The physiologic mechanism involved in the sense of hearing includes the 



ear, the acoustic nerve, the acoustic tract (the lateral fillet or lemniscus), the 

 acoustic radiation, and nerve-cells in the cortex o the temporal lobe. 



Peripheral stimulation of this mechanism develops nerve impulse which, 

 transmitted to the cerebral cortex, evoke the sensation of sound and 

 ins Qualities intensity, pitch, and timbre. 



The specific physiologic stimulus to the terminal organ, the organ of 

 Corgis the impact of atmospheric pulsations of varying energy and rapuhty. 



THE PHYSIOLOGIC ANATOMY OF THE EAR 



The ear the organ of hearing, is lodged within *e petrous portion of 



(Fi Th 3 eExternal Ear.-The external ear consists of the ***** or auricle 



and the external auditory canal. cartilage which 



The Pinna. The pinna is composed of a thin layer ol caruiag 



5TLr a^itAelow the Liter, a 



d "SSS^ 



glands. They secrete cerumen or ear- 



IS^ii^sSS'Si-SSlBSE 



external auditory canal and the ^^^L long in its antero-posterior 

 though wider above than J^l w - ^ portion is known as the attic. The 

 and vertical diameters. _ ^ n U ^ s e ter i or i y w ith the mastoid cells, anteriorly 



with the" ph^ynx ^S^J^^ the tympanic ca vity and 



1 ne tLUSi acni'd A^^^nir^f^T QQtVip Eustacnian tuue. IL 



