We discriminate, then, between the sense of touch and that of mere feeling. Most probably all animals, even the lowest mollusks, feel,--nay, even animals in which no nerves are to be discovered, as the acalephæ, or jelly fishes; but touch is a refinement upon feeling, which is restricted within certain zoological bounds. A learned writer says: "The conditions on which the perfection of the sense of touch depends are, first, an abundant provision of soft papillæ, supplied with numerous nerves; secondly, a certain degree of fineness in the cuticle; thirdly, a soft cushion of a cellular substance beneath the skin; fourthly, a hard resisting basis, such as that which is provided in the nails of the human fingers; and lastly, it is requisite that the organ be so constructed as to be capable of being readily applied, in a variety of directions, to the unequal surfaces of bodies, for the closer the contact, the more accurate will be the perceptions conveyed. In forming an estimate of the degree of perfection in which the sense is exercised in any particular animal, we must accordingly take into account the mobility, the capability of flexion, and the figure of the parts employed as organs of touch."[21] [21] Dr. Roget. This is decidedly true as regards the higher orders of creation; but let us look at insects--do not bees, and wasps, and flies feel? can we watch a fly brushing its head and wings, and rubbing its little paws against each other, without an assurance that it enjoys the sense of touch? and what shall we say of the spider, that feels at each thread, and "lives along its line?" Surely its sense of touch must be sufficiently acute; yet it is limited to a certain given object, and the spider gains only that information which bears upon its animal necessities. But the sense of touch gives to man a number of the properties of matter, which he retains as abstract ideas, such as dimension, form, condition of surface, hardness, softness, elasticity, compressibility, fluidity, quiescence, motion. In many and most important respects it assists the eye; and, indeed, the senses of sight and of touch appear to be correctors and supporters of each other. As in the case of every other sense, accuracy is greatly improved by habit, yet the qualities of matter, under the dominion of touch, are ascertained in so correct a manner that we are scarcely ever deceived by the knowledge thus acquired.