OF TOUCH, TASTE, AND SMELL THE sense of touch is the most important after those of sight and hearing. The term has been frequently applied indefinitely, to express every sensation of impression which could not be referred either to sight, hearing, smell, or taste. The sensations of touch are, however, strictly speak ing, merely those of resistance, excited by a body pressing upon certain portions of the skin. Although every part of the surface seems to possess some degree of touch, yet there are specific organs by which it is exercised with pe culiar acuteness and delicacy—such are the points of the fingers in the human subject, and in many animals, the lips and the tip of the tongue. The greater sensibility of the fingers is probably owing principally to the finer texture of the skin, and to the greater quantity of nervous matter distributed to the part ; but it must be partly ascribed to our dexterity in recognizing the sensations impressed upon it, which we acquire by habit : for there are examples of individuals born without hands, who.acquire a delicacy of feeling in the toes not very much inferior to that of the fingers.
Some eminent metaphysicians have advanced the opi nion, that the touch is the most certain of all the senses, and that it is essentially useful in correcting the errors of the sight and hearing. This remark is, to a certain extent, true, for the organ of touch is necessarily brought into contact with the body upon which it acts, whereas, in the action of the eye and the ear, the impression is conveyed by a peculiar medium, which may, and frequently does, affect the nature of the original impression. But, although we may allow that the perceptions derived from the touch are more correct, we must admit that they are very limited, and that our knowledge would be confined within a very narrow range were we to acquire no ideas through any other medium. An interesting detail has been lately pub lished, of a young man in this country, who appears to have possessed a competent share of intellect, but was born both blind and deaf, the principal part of whose knowledge of the external world has therefore been derived from the sense of touch. It is curious to observe with what patience
and perseverance he has laboured to obtain a certain de gree of knowledge of the external world, cut off, as he ne cessarily is, from almost all intercourse with his fellow creatures ; while, at the same time, we must be strongly impressed with the very limited information which, with all his exertions, he has been enabled to acquire.
We so seldom employ the touch without likewise mak ing use of some of the other senses, that it is difficult to determine what ideas we originally derive from it, and what are its acquired perceptions. Locke appears to be suc cessful in showing that the conception of solidity is altoge ther gained by the touch, but we think that the ideas of motion and figure originate at least as much from visible as from tangible impressions. The touch has been gene rally supposed to aflOrd us the ideas of distance and exten sion; but with respect to these we are much aided by the sight, and also by the peculiar sensations that originate in the motion of the joints—sensations that are essentially different from those that depend upon resistance.
The senses of taste and smell are much less important to our existence, and to our intercourse with the external world, than those of sight, hearing, and touch. In the hu man species they are to be regarded as rather conducive to our gratification than to our utility ; but in the lower animals they are of more importance, as being connected with some of the instincts which are directly essential to the existence of the individual, and to the continuance of the species. They are deserving of notice as affording some remarkable instances of the power of association, partly as derived from very early impressions, and partly as acquired by subsequent habits. It appears indeed pro bable that certain flavours and odours are naturally agree able to us, but, at the same time, our daily experience proves, that our tastes in this respect are principally ac quired.