264 PHYSIOLOGY CHAP. 



improves the auditory function, as Urbantschitsch showed experi- 

 mentally. He conveyed the sound of the Neef's hammer of an 

 induction coil to the ear by telephone. The position of the 

 secondary coil at which the sound was not heard was taken as 

 zero, and the rest of the scale was divided into 100 parts, from 

 zero to the maximum intensity audible, when the following 

 results (A, B, C, D) were obtained from four individuals : 

 Pushing up the coil from zero : 



A B C D 



Right ear 10 6 8 55 



Left ear 10 7 8 55 



Both ears 5 3 5 51 



This shows that binaural is much finer than uniaural hearing. 



Tones and noises conducted by bone and not by the tympanic 

 membrane are as a rule projected inwards and not outwards. 

 This is observed under water, when the auditory passages are free 

 from air (E. H. Weber). The note of a tuning-fork placed on 

 the head is heard in the ear nearest to it. The limit of localisation 

 for the two ears should correspond exactly with the median plane, 

 but in practice this is rarely so, because the auditory aeuteness 

 of the two ears differs to some extent, even under normal condi- 

 tions (Urbantschitsch). 



BIBLIOGRAPHY 



For complete Monographs of Physiological Acoustics, containing many quota- 

 tions, see the following : 



E. CLADNI. Die Akustik. Leipzig, 1830. 



J. MILLER. Handbuch d. Physiol. d. Menschen. Coblenz, 1840. 



E. HARLESS. In Wagner's Handwbrt. d. Physiol. (article " Horen "). Brunswick, 



1853. 



V. HENSEN. Hermann's Handbuch d. Physiol. iii. Leipzig, 1880. 

 C. STUMPF. Tonpsychologie. Leipzig, 1890. 

 S. v. STEIN. Die Lehre von den Functionen der einzelnen Teile des Labyrinths. 



Jena, 1894. 

 H. v. HELMHOLTZ. Die Lehre von den Tonempfmdungen, 5th ed. Brunswick, 



1896. 



F. BEZOLD. Die Funktionspriifung des Ohres. Wiesbaden, 1897. 



K. L. SCHAEFER. "Der Gehorsinn," Nagel's Handbuch d. Physiol. d. Menschen, 

 iii. Brunswick, 1905. 



Functions of the Tympanic Apparatus and its Muscles : 



HELMHOLTZ. Pfliiger's Arch, i., 1868. 



MACH. Ber. d. Wiener Akad. xlviii., 1863 ; 1., 1864 ; Hi., 1865 ; Ixvi., 1872. 

 LUCAE. Arch. f. Ohrenheilk. i., 1864. 

 BUCK. Arch. f. Augen- und Ohrenheilk. i., 1870. 

 SCHAPRINGER. Ber. d. Wiener Akad. Ixii., 1870. 

 BURNETT. Arch. f. Augen- und Ohrenheilk. ii., 1872. 

 MACH and KESSEL. Ber. d. K. Akad. z. Wien, Ixvi., 1872 ; Ixix., 1874. 

 POORTEN. Monatsschr. f. Ohrenheilk., 1874. 



POLITZER. Arch. f. Ohrenheilk. i., 1864 ; iv., 1869 ; vi., 1873 ; ix., 1875. 

 HENSEN. Arch. f. Anat. u. Physiol., phys. Abteil, 1878. Pfliiger's Arch. Ixxxvii., 

 1901. 



