360 OF HEARING. 



The eye is the ear is in a philosophical sense the time organ ; that, the func- 

 organ of space, ^ion of the eye being the estimation of extents, the position 

 of objects, their sizes and apparent distances, this apparatus is, in reality, 

 the space organ, its indications in this particular being rendered more 

 perspicuous and more intense by its quality of being affected by varia- 

 tions of color ; that as the tactile mechanism is affected by extraneous 

 Touch is for ^ orces sucn as pressures, estimating their degree of power, and 

 pressure and being likewise influenced by things which are at a distance, 

 temperature. ^ tem p eratures O f wn i cn are different from the standard 

 which it observes, but not by electrical, magnetic, or luminous agencies, 

 we may infer that its functions are limited to a relation with mechanical 

 Smell and taste powers, strictly speaking, and to heat; that smell and taste, 



for chemical though conveniently treated of as separate functions, de- 

 qualities of gas- . * . ' 

 es and liquids pendent on separate organs, are, in reality, allied in the de- 



respectiveiy. termination of the chemical peculiarities of bodies, and re- 

 spectively adapted to the appreciation of those peculiarities, according as 

 the substance presented may have the gaseous or liquid form. 



OF HEAEING. 



The organ of hearing is composed of three parts, the external ear, the 

 tympanic cavity or tympanum, and the labyrinth. 



The external ear consists of, 1st. The pinna, which is for the purpose 

 Oftheexter- f collecting soniferous waves, and directing them into, 2d. 

 nal ear. The meatus auditorius or auditory canal, a tube about an inch 

 long, and extending to the tympanum. It is not perfectly cylindrical, 

 its vertical diameter being the greatest, and it is curved so as to be con- 

 cave downward. The interior is protected by hairs, and by a waxy se- 

 cretion of the ceruminous glands. 



The tympanum, tympanic cavity, or middle ear, is within the petrous 

 Ofthetympa- tone. It is bounded exteriorly by a thin oval membrane, 

 num - the membrana tympani, which is placed obliquely across the 



meatus, at an angle of about 45 degrees, its outward plane looking down- 

 ward. Across the tympanum there is a chain of three small bones, the 

 malleus or hammer,, the incus or anvil, and the stapes or stirrup. The 

 malleus is attached by its handle to the membrana tympani, and the 

 stapes, which is at the other extreme of the chain, is fastened by its foot- 

 plate to the membrane of the fenestra ovalis. To the short process of 

 the malleus, the tendon of the tensor tympani is attached, and to the neck 

 of the stapes the stapedius. Besides these, other muscles of the tympa- 

 nic cavity may be doubtfully mentioned, as the external muscle or laxa- 

 tor tympani, and the laxator tympani minor. Into the tympanic cavity 

 there are ten openings, of which the more important ones are, 1st. That of 

 the meatus auditorius ; 2d. The fenestra ovalis, which is of an elliptic 



