TOPOGRAPHICAL ANATOMY OF THE EAK. 151 



ter passed through the Eustachian tube into the tympanic 

 cavity, or by the external meatus. In addition, there are 

 other well-established clinical observations, mentioned by 

 Wreden, which sustain the theory of muscular contraction, 

 and are opposed to the idea of direct stimulation of the au- 

 ditory nerves. 1 



The facts just stated show that there is no positive evi- 

 dence of the production of impressions of sound by gal- 

 vanic stimulation of the auditory nerves ; while it appears, 

 from experiments which we have already cited, that these 

 nerves are not endowed with general sensibility. The re- 

 sults, then, as regards the auditory nerves, are simply nega- 

 tive. Were it possible to expose these nerves to mechanical 

 or galvanic stimulation, in the human subject, without in- 

 volving other parts, we might arrive at some definite conclu- 

 sion ; but the difficulties in the way of such an experiment, 

 it must be admitted, have thus far proved insurmountable. 



Topographical Anatomy of the Parts essential to the Appre- 

 ciation of Sound. 



Perfect audition requires the anatomical integrity of a 

 very complex apparatus, which, for convenience of anatom- 

 ical description, may be divided into the external, middle, 

 and internal ear. A correct appreciation of the physiology 

 of these parts demands, as a necessary preparation, a knowl- 

 edge of their physiological anatomy : 



1. The external ear includes the pinna and the external 



1 WREDEN, Bdtrage zur Begrundung einer Lehre uber die elektrische Rdzung 

 der Binnenmuskeln des Ohres. St. Petcrsburger medidnische Zeitschrift, St. Pe- 

 tersburg, 1871, Neue Folge, Bd. it, S. 440. 



A very full review of the literature of this subject, with copious references, 

 is given by Wreden (Ein Fall von Verbrennung der PaukenhoJde, etc. St. Pe- 

 tersburger medicinuche Zeitschrift, St. Petersburg, 1871, Neue Folge, Bd. i., Se- 

 paratabdruck, S. 86, et seq.) A reply, by Schwartze, to the experiments and 

 conclusions of Brenner is published in the Archiv fur Ohrenheilkunde, Wiirtz- 

 burg, 1864, Bd. i., S. 44, et seq. ; and a review of Brenner's theory and the reply 

 of Schwartze was published by Hagen, in 1866. (Praktische Bdtrage zur Ohren- 

 heilkunde, Leipzig, 1866.) 



