No. I.] THE VERTEBRATE EAR. 305 



with the cushion of air inclosed between it and the water, which 

 may enter only part way into the meatus auditorius externus and 

 incompletely fill it. The inflow of many of the constant stim- 

 uli from without being prevented, the transmission of internal 

 vibrations arising from the cardiac pulsations and the rush of 

 blood through the blood-vessels, the rustling sounds due to the 

 passage of air currents through the pulmonary passages and 

 other respiratory ways, being greatly increased, one is able 

 to hear with remarkable distinctness the great amount of noise 

 of several kinds which these physical processes make. 



The very remarkable noise produced, for example, by the 

 contraction of the temporal and masseter muscles resembles 

 very closely the incessant clatter of a large number of tele- 

 graphic instruments being operated simultaneously. There is 

 a distinctive character possessed by these sounds, due entirely, 

 I believe, to the greater intensity of the vibrations of liquid and 

 solid media over those of gases. 



It is said that the transmission of vibrations by means of the 

 bones of the skull is of no importance to animals above the 

 fishes, but that in these (possessing no external ear) the head 

 bones play a very important part in the transmission of sound ; 

 in fact, it is about the only means for the transfer of the sound 

 waves. This is certainly true, so far as concerns the main uses 

 to which the human ear is put, but we cannot doubt that the 

 ear plays an important part in keeping the internal organs in 

 normal condition of work by sending in a continuous stream of 

 stimuli due to pulsations of the circulation, respiration, and all 

 of the many processes which cause vibrations either in the 

 lymph channels or the bone about the ear. The musical sense 

 as it exists among civilized and cultivated races is a result of 

 the association of ideas and of tone production, and not of a 

 perfection in the apparatus for tone perception in the ear. 



