884 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



chain of bones and reach the membrane of the fenestra ovalis. From 

 that point they are communicated to the perilymph, thence to the 

 membranous labyrinth, thence to the endolymph, and finally to the 

 otoliths, -which serve to increase the vibratory impression upon the 

 nerve of hearing. This transmission of sound from the exterior and its 

 recognition in the centre plainly involves important considerations with 

 regard to the propagation of sounds. ' 



Sounds are transmitted in three ways : first, by reciprocation ; second, 

 by sympathetic vibration; and, third, by conduction. As regards vibra- 

 tions by reciprocation, if two strings of equal tension, length, and 



Fig. 408.— I. Section Through the Uncoiled Cochlea. II. Section 

 Through the Terminal Nerve-Apparatus of the Cochlea, after 

 Heusen. (Munk.) 



I. F. r.. Fenestra rotunda ; 77, the helicotrema; St.. the stapes. II. 2. Ilusch Ice's process ; ht, basilar 

 membrane; f. Corti'9 arch: g, supporting ceils; h, cylindrical cells; i, Deiter's hair-cells; c, lncmbrana 

 tectorial n, nerve-fibres; n>, non-medullated nerve-fibres. 



density be stretched side by side each one is capable of producing the 

 same musical tone when thrown into vibration. Now, when one of these 

 strings is thrown into vibration the other will fall into vibration by 

 reciprocation, although it be not itself touched. The same thing will 

 occur when the same musical note is sounded on another instrument, as 

 the tuning-fork, if in sufficient proximity. If one of the strings be 

 stretched tighter than the other a higher musical note will be produced. 

 If this string be thrown into vibration near one of lower note the latter 

 will be divided into equal divisions, which are likewise thrown into vibra- 

 tions of reciprocation, and increased sound will result. If, however, 



