HEARING. 555 



ear. The vibrations proceeding from the air within the mouth 

 cannot be transmitted so easily to the branches of the acoustic 

 nerve distributed to the vestibule and semicircular canals, because 

 these, spread out as a sacculated and tubular membrane, are stu- 

 diously separated from the bones by a liquid secretion or loose 

 cellular membrane. Weber therefore concludes that the cochlea 

 is intended to place the extremities of the acoustic nerve in con- 

 nection with a vibrating solid. On the other hand, he concludes 

 that the use of the semicircular canals is to be in connection 

 with a vibrating fluid and receive the impulses of the air through 

 themeatus auditorius. Because, 1. the vestibule and semicircular 

 canals have a solid communication by the chain of bones with the 

 membrana tympani, whose vibrations are at once imparted by 

 them to the membrana of the fenestra ovalis ; whereas there is no 

 such direct communication between the membrana tympani and the 

 fenestra rotunda. 2. The membrane of the semicircular canals 

 and vestibule seem more easily thrown into vibrations by the fluid 

 around them than the lamina spiralis of the cochlea. The latter 

 also, however, is enabled to receive impulses from the air, by the 

 membrane of the fenestra rotunda communicating the vibrations 

 which occur in the tympanum, and by the opening of the cochlea 

 into the vestibule causing the vibrations of the fluid of the vesti- 

 bule to be at once propagated to the cochlea. 



Weber states that Scarpa was the first to discover the remark- 

 able difference in consistence and texture which exists between 

 that portion of the acoustic nerve which supplies the cochlea, and 

 that which is distributed to the vestibule and semicircular canals. 

 The latter, surrounded on all sides by a fluid, are soft and pulpy, 

 evidently fitted to receive impulses from a fluid : the former, on 

 the contrary, fine and ramified, as evidently adapted to the re- 

 ception of vibrations from a solid. 



I must state that Professor Wheatstone above ten years ago 

 made experiments similar to those of Weber and with the same 

 results. 1 His views respecting the functions of the semicircular 

 canals differ from those advanced by Weber. He maintains that 



* See his Experiments on Audition in the Journal of Science, New Series, 

 vol. ii. p. 67. 1827. Some curious and original observations and experiments 

 will be found in a paper by Dr. Wollaston, Phil. Trans. 1820; and some inter- 

 esting facts in Savart's Memoir. 



