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“ Life speeds away
course, the tremulation excited in them by the motion of the air are comparatively weak. Young children accordingly are extremely fond of noise. It arouses their attention, and conveys to them the agreeable sensation of mind ; but feeble sounds are not perceived, which gives infants, like deaf persons, the appearance of dullness or want of intelligence.
146. Why are we compelled to use both ears in order to determine the direction of a sound ?
Because every sound comes more directly to one ear than to the other, and it is only by comparing the intensity of the two impressions, that we are capable of deciding whence the sound: proceeds.
147. If we close one ear perfectly, and cause a slight noise to be made in a dark place at a short distance, it would often be impossible to determine its direction; in using both ears this could be determined. If a person wakes in the night and hears a sound but cannot tell from what quarter it proceeds, he will turn his face full in the direction from which he supposes the sound to come, thus availing himself of both ears; having determined this, and wishing to distinguish the sound, he will incline one ear only for this purpose.
148. Why do persons who are partially deaf place their hand behind the ear, in order to hear more distinctly?
Because the hand thus placed acts upon the same principle as the sounding board ; that is to say, the sound reverberates against it, and penetrates the ear, instead of passing by, which it would do, if no barrier existed.
149. Why will a person who is partially deaf frequently hear more distinctly when addressed in a moderate tone, than when called to in a loud voice ?
Because in many cases of defective hearing, the impaired organs are so extremely sensitive, that a loud voice acts like a concussion upon them, and thus defeats its own end; whereas a moderate tone adapts itself to the limited power of hearing, and thus makes a suitable impression.
“A good nose is requisite, also, to smell out work for the other senses." ,
150. Why may the ticking of a watch be heard distinctly when it is placed against the teeth ?
Because sound is capable of being produced by the vibration of solid bodies without the intervention of the atmosphere, and in this instance the sound is conveyed from the teeth, through the bones of the face and the head, to the auditory nerves.
151. How is the sense of smell produced ?
When we put a flower or a sweet scent of any kind to our nose and enjoy the smell of it, it is because the nerves lining our nostrils are touched by very small particles which fly off from the flower or scent. In the same way unpleasant smells are detected by minute noxious particles floating in the air, coming in contact with the nostrils.
152. Why do persons “sniff up the air” when any agreeable odours are floating in it?
Because when the nostrils are thus exerted, they act as a species of syphon, and withdraw a larger amount of the odour from the atmosphere than they otherwise would, so that the action of sniffing increases the pleasurable sense thus imparted.
153. Why does closing the mouth increase the sense of smell ?
Because under that condition the respiratory current is drawn exclusively through the nose. On the contrary, when we wish to avoid a disagreeable odour, the end may be effected by keeping the mouth open, through which respiration will chiefly take place, and very little through the medium of the nose.
154. Why are the organs of smelling and of tasting situated So near to each other?
Because the vicinity of these two senses forms a double guard in
• A next in order sad, Old Age we found :
His bear) all hoar, his eyes hollow and blind :
the selection food. Were they placed in distant parts of the body, they could not so readily give mutual aid.
155. Why is taste the least deteriorated by age of any of the senses ?
Because so long as the body exists it must necessarily be fed, and the organ by which this process is primarily accomplished is mercifully spared, while other senses less essential are subjected to decay.
156. Why is touch considered to be the most important of all the senses?
Because by touch we are enabled to know with greater certainty the properties of bodies ; our hearing, seeing, and smelling may frequently deceive us and lead us into error, touch seldom does this, and in all cases of doubt when the other senses are engaged, touch steps in as umpire, and resolves the difficulty.
157. The extreme sensibility of the touch of the blind is well known. A blind person deciphering a book by the aid of touch will, in general, read with fewer mistakes than are made by persons of ordinary intelligence when perusing a book by the aid of their sight. There are many remarkable instances of the intensity with which one portion of the senses may be exercised, and especially that of touch, when others are wanting ; ordinary faculties taking upon themselves extraordinary functions, and thus in a great measure compensating for the deprivation which it has pleased Providence to inflict. A case in point is furnished by the following narrative :
James Mitchell, the son of a respectable parish minister in the County of Elgin, was deaf, dumb, and blind from birth. As he grew up, he discovered a most extraordinary acuteness in the senses of touch and smell, being very soon able by these to distinguish strangers from the members of his own family, and any little article that was appropriated to himself from whať belonged to others. In childhood the most noticeable circumstance relating to him was an eager desire to strike upon his fore-teeth; this he would do for hours. When a stranger arrived, his smell would invariably inform him of the circumstance, and direct him to the place where the stranger was, whom he proceeded to survey by the sense of touch. In the remote situation where he resided male visitors were the most frequent, and therefore the first thing he generally did was to examine whether or not the stranger wore boots ; if such were the case he would immediately quit the stranger and proceed to the stable, accurately examining the whip, and handling the horse with great care and the utmost seeming attention. It has occasionally happened that “ One touch of Nature makes the whole wo.Id kin.”-SHAKSPERE.
visitors have arrived in a carriage, and on such occasions he has never failed to go to the place where the carriage stood, examining the whole of it with much anxiety, and trying innumerable times the elasticity of the springs. When he felt hungry he would approach his mother or sister, touching them in an expressive manner, and pointing to the apartment where the victuals were usually kept. If a dry pair of stockings were wanting, he would point to his legs, and, in short, intimate his various wishes in a similar way. On one occasion a pair of shoes was brought, and on attempting to put them on he found they were too small. His mother took them and locked them in a closet. Soon after a thought seemed to strike him; he contrived to obtain the key of the closet, opened the door, took out the shoes, and put them on the feet of a young lad who attended him, and whom they fitted exactly. When he happened to be sick and feverish he would point to his head, or take his mother's hand and place it opposite his heart. He never attempted to express his feelings by utterance, exeept when angry, when he would utter a loud bellow. Satisfaction or complacency he expressed by patting the person or object which had excited that feeling. His smell being wonderfully acute he would be frequently offended through that sense when other persons near to him smelt nothing unpleasant. His elder sister seemed to have a much greater ascendancy over him than any other person. Touching his head with her hand was the principal method she employed in signifying her wishes to him respecting his conduct. This she did with various degrees of force and in different manners, and he seemed readily to understand the intimation intended to be conveyed.
158. Why is the sense of touch more vivid when the circulation is warm and active than when it is chilled and stagnant?
Because the papillæ are dependent for their life and action on a constant supply of blood, when, therefore, the nerves receive an abundant supply of the stimulating fluid the sense of touch becomes proportionately acute; and when this suprly is stinted or withheld, sensation may in some cases become so blunted, as to allow wounds to be inflicted without exciting pain.
159. Why is the sense of touch sometimes untrustworthy ?
Because it has its delusions like tne other senses, so much so, that a body may be imagined to be felt, and yet have no real existence.
160. The following illusion of an extraordinary kind, which cannot be corrected even by the sight, proves that the senses alone unaided by the reasoning powers are not to be trusted; cannot indeed be believed on all occasions :—If we place on
“ The universal cause
a table, or on the palm of the hand, a marble, or any other small globular body, and crossing it alternately with the fore and middle fingers so disposed that the marble shall touch only the outer edges or surfaces of the two fingers, the person will believe that he touches two marbles, although he knows that only one is present. The explanation of this illusion is as follows: The mind refers, involuntarily, all sensations experienced at different parts of the body to the position in which such parts are usually placed. Now the crossing of the fingers does not prevent us feeling either of them in contact with the marble, as if they were placed naturally side by side. But in the habitual position of the fingers side by side, it is impossible that the outer edges of any two fingers can be at the same time placed in sufficient contact with a single marble or other similar rounded body; and thus when such contact actually takes place simultaneously, by the contrivance of crossing the fingers, then the mind involuntarily believes the thing to be impossible, takes it for granted that two marbles, not one, must be present ; and hence arises the sensation and perception of two distinct bodies.
CLASSIFICATION OF THE VARIOUS ANIMALS.
161. Why are animals arranged by naturalists into classes, orders, sub-orders, families, &c. ?
Classification prevents the necessity of frequently and fully describing any animal referred to; it ensures correct identity in the observations and communications of naturalists. It also answers as a sort of dictionary wherein, from the properties of things, we proceed to discover their names, thus forming the inverse of ordinary dictionaries, where the names direct us to the properties But no arrangement of animals can be perfect ; first, because we may not be acquainted with all the species ; secondly, because of some of the species we may know very little ; and, thirdly, because of those which we know best, the greater part are known as more or less domesticated; and, further, because the