HEARING IN FISHES. 169 



which are entirely inaudible to others, whose hearing is 

 nevertheless acute enough in regard to common sounds ? 

 Dr. B. Yes, there are a few sounds of this kind, 

 but they are all extremely low. Different sounds have 

 the power of affecting the ear that is, the physical or- 

 gans, agreeably or disagreeably. The harsh grating of 

 metals or other hard bodies on one another, is offensive 

 to every ear ; the bubbling of a brook, and the song of 

 birds, are on the contrary, agreeable to all. The sensa- 

 tion is also greatly modified by the manner in which 

 sounds are combined. Sounds made from musical in- 

 struments at random by the unskilled and ignorant, are 

 always unpleasing ; but when arranged in a certain or- 

 der, and directed by skill and taste, they are a source of 

 the most delightful sensations. 



Emily. What is the cause of the great difference 

 that exists among people, in regard to the manner in 

 which they are affected by musical sounds ? Is it any 

 difference in the structure of the ear ? We hear of peo- 

 ple having a. good ear, and a bad ear for music* 



Dr. B. This language is literally incorrect, people 

 have confounded that mere physical delight which some 

 sounds will produce in every one, with that internal sat- 

 isfaction which arises from the perception of harmony 

 between musical sounds. The former is altogether 

 physical, like the pleasure derived from the sense of 

 smell and taste ; but the latter originates from a distinct 

 faculty of the mind, which, like those that give an ex- 

 cellence to some in poetry, painting and other arts, is a 

 gift of nature not bestowed on all. 



In examining the oigan in the inferior animals, we see 

 its different parts vanishing one after another, until we 

 come to some of the shell-fishes, where we find neither 

 external ear, tympanum, nor bones, but merely some 

 membranous sacs, in which are expanded the minute 

 filaments of the auditory nerve. Fishes, and some rep- 

 tiles have no external passage to the ear ; the only com- 

 munication is by the Eustachian tube. 

 15 



