INTRODUCTION. 



The sense of taste aids that of smell in the choice of food, and, 

 among the lower mammals, coinciding with their natural instincts, it is one 

 of the tests, according to which they receive or reject whatever is sub- 

 mitted to it ; the disagreeable being hurtful, the agreeable, except in 

 rare cases, innocent and proper. Man has not these instincts, or, if he 

 have, it is during the helplessness of infancy only ; his like or dislike of 

 certain viands is, to a great extent, the result of habit. The Greenlander 

 relishes train oil and half-putrid fish, or the rank flesh of the Whale, from 

 which we should turn with disgust. 



So far, then, from the foregoing observations, may be understood the 

 nature of those recesses of the face, in which are seated the organs of 

 sight, smell, and taste. With regard to the organs of hearing, they are 

 contained in certain cavities of the temporal bone, of a curious and intri- 

 cate arrangement, which cannot be altogether passed over without some 

 explanatory notice. In Man, it may be premised, the temporal bone 

 consists of two portions ; viz., the squamous and the petrous portion : 

 the squamous portion is, in shape, somewhat like an oyster-shell, and 

 conjoins with the parietal and a portion of the sphenoid, to form the 

 lateral wall of the skull ; the petrous portion, an irregular mass of bone,, 

 enters into the base of the skull, and is hollowed, to contain the organs 

 of hearing : in addition to the petrous portion, may be noticed, the mas- 

 toid portion, or process, as it is termed, which is also filled with cells 

 communicating with the internal ear. At an early period of existence 

 these parts are all distinct, but they afterwards become consolidated. 

 In many of the lower mammals, however, the temporal bone remains 

 permanently divided into its primitive elements. 



The ear consists of an external cartilaginous organ, or concha, the 

 shape and form of which need not be now particularized, and of an internal 

 apparatus. From the external ear, or concha, a funnel-shaped canal, 

 termed the meatus auditorius, leads into the internal chambers ; it curves 

 gently inward, till its course is stopped by a membrane extended across 

 it, and separating it from the cavity beyond : this membrane, from its 

 resemblance to the parchment stretched over a drum, is called the mem- 

 brana tympani ; the cavity beyond being called the tympanum. The 

 membrana tympani consists of two films of delicate cuticle, continued 

 from the lining of the meatus auditorius on one side, and of the tympanum 

 on the other, with minute radiating muscular fibres between them : by 

 means of this fine muscular apparatus, its tension can be varied, according 

 to the strength or character of the vibrations of the atmosphere ; and, as 

 these fibres are inserted into the extremity of the first of a curious series 

 of little bones, their action, determined by the stimulus they receive from 

 the atmospheric vibrations, adjusts these bones in an according ratio. 



The tympanum is an irregular cavity filled with air, and has three re- 



