386 THE HARMONIES OF NATURE. 



apparatus, instantly communicate the impressions they have 

 received with the most admirable precision to the brain. 



While the optic nerve holds up to us the magic mirror in 

 which Nature appears in all her beauty, the auditive nerve 

 opens to our perception the wondrous realms of sound. The 

 undulating atmospherical vibrations produced by the voices of 

 a choral band, or by the instruments of an orchestra, strike its 

 delicate membranes and awaken musical sensations, which, 

 transmitted to the soul, attune it to joy or to sorrow, rouse 

 it to martial ardour, or exalt it to feelings of the deepest 

 piety. 



In a similar manner the olfactory and gustative nerves, 

 proceeding from other parts of the brain, spread out like 

 pieces of tapestry over the nasal cavities, or over the surface 

 of the tongue and palate, and, stimulated by the smelling 

 gaseous particles that may be mingled with the air we respire, 

 or by the sapid liquid substances we swallow, communicate 

 their various impressions to the brain. 



While the senses of vision, hearing, taste, or smell thus each 

 depend upon a single pair of nerves seated in the brain, and 

 confined to a comparatively narrow space, the sense of feeling 

 extends over the greater part of the body. The face, the mouth, 

 the nasal cavities feel by means of a pair of nerves proceeding, 

 like those already mentioned, immediately from the brain ; but 

 all the other sensitive nerves that ramify over the body, though 

 communicating with that central organ, first pass through the 

 spinal marrow, whose posterior columns they form, and which 

 runs like a thick cord from the brain downwards through the 

 spinal canal. From the spinal marrow they then emerge at 

 regular intervals in thirty-one pairs, which, branching out, each 

 supply a certain part of the body with the necessary power of 

 feeling external objects. In those parts where a greater nicety of 

 touch or acuteness of sensation is unnecessary, or would have been 

 more irksome than useful, the sensitive fibres are more thinly scat- 

 tered as, for instance, on the back ; or they may even be entirely 

 wanting, as in many internal parts of the body. Their chief 

 distribution is in the skin, where they not only enable us to 

 distinguish many of the physical properties of external objects 

 such as their degree of solidity, their weight, the soft or rugged 

 nature of their surface but preserve us, moreover, like trusty 



