156 ANTENNE OF INSECTS. again, it is the corpus mucosum which gives them their earthy covering, a proper cuticle being found exterior to it, as in the sea-urchin, the star-fish, and all the testaceous tribes: the sharp prickles, also, on the shell of the sea-urchin, as well as the hairs of the earth-worm, and numerous other animals of this tribe, are merely modifications of the same substance. A proper cutis seems, indeed, to be wanting in the corallines, as well as in some other animals of quite the lowest orders; but in the testaceous tribes, as the oyster, the cloak is probably a modification of this part, and it is accordingly upon this, or some corresponding organ, that the tentacula, or immediate instruments of touch, are commonly met with. The perspiration from the surface seems to bear the same relation to touch as the saliva bears to taste; and there are, therefore, few animals which do not perspire in one form or another. In some of these tribes, as the sea-blubber, the perspired matter is said to be luminous; and it is to this cause that the sparkling appearance of the sea by night in some places has been attributed. In insects, the cuticle is always membranous; while it is. the corpus mucosum which constitutes their horny or calcareous sheaths, and forms, also, in some, as spiders, flies, gnats, bees, and butterflies, the fine hairs, feathers, or scales, with which they are in certain parts invested. The proper cutis, again, is below this, constituting, in the lobster, for example, its membranous pellicle. This part is, however, so completely defended, for the most part, from the contact FIG. 79. VARIOUSLY FORMED ANTENNE OF INSECTS. THE CUTICLE OF FISHFS AND REPTILES. 159 of external substances, that to most insects are given in addition antennæ, palpi, cirrhi, &c., called in general feelers, situated commonly about the mouth, and the chief seat, in them, of the function of touch. The cuticle is membranous also in fishes, and immediately invests their scales, as well as the bristles of the stickleback, the tubercles of the sturgeon, &c., all which are formed by the corpus mucosum. Under this is the cutis. Not only are the smell and taste of fishes very acute, but their touch not less so than that of animals in general. It is astonishing, however, what an extreme degree of heat some fishes can bear. In the thermal springs of Bahia, in Brazil, many small fishes were seen swimming in a rivulet which raised the thermometer eleven degrees and a half above the temperature of the air. Sonnerat found fishes existing in a hot spring at the Manillas at a hundred and fifty-eight degrees Fahrenheit; and Humboldt and Bonpland, in travelling in South America, perceived fishes thrown up alive, and apparently in health, from the bottom of a volcano, in the course of its explosions, along with water and heated vapour that raised the thermometer to two hundred and ten degrees, being but two degrees below the boiling point. The bodies of most fishes are covered with small brilliant plates of a horny nature, called scales; but in certain kinds these are wanting, as in the turbot, in place of which are found osseous or cartilaginous protuberances in some species, and in others a very smooth skin, without scales or rugosities, but covered with a thick gelatinous secretion. It was observed by Steno, in the skate, that this slimy matter was poured out from numerous orifices regularly placed near the surface; and Dr. Monro has recorded his discovery of a very elegant structure for the preparation of this mucus between the skin and muscles. The secretion is so viscid that it is with great difficulty pressed out. There is a species of carp- the rex cyprinorum of Linnæus-that seems to hold a middle place between the rough and smooth-skinned fish; the upper part and back is covered with scales, while these are altogether wanting on the lower part and belly. In reptiles the cuticle is either membranous, or, as in the frog, consists merely of mucilage, as it does in many worms already noticed. The corpus mucosum in these animals assumes the form either of a soft, viscid substance, as in frogs; of a horny shield as in tortoises; or of scales, as in serpents and most lizards; some of the latter, however, as the crocodile and alligator, have it again in the form of hard plates, like the shields of tortoises. It is of the corpus mucosum, also, that the claws of such reptiles as have them are constituted The proper cutis is situated under this; and as the papillæ sai CUTICLE OF BIRDS, ETC. re most numerous about the soles of the feet, we must it is in this part principally that the touch of reptiles iration of reptiles is in general very copious; that of the , for example, being so much so, as to extinguish flame, and thus to have given rise to the fable of its being capable of living in the fire. In some, as the toad, the perspired matter is of a poisonous quality; and in one kind of lizard it is so acrid as to blister the fingers. In birds, the cuticle is again membranous; while the corpus mucosum assumes the form, upon the mandibles, of a bill; upon the body in general, of feathers; upon the legs, of scales; and at the extremity of the toes, of claws. Under this is the cutis, which, abounding in papillæ, most in general below the bill, particularly in the swan, goose, and duck, may be presumed to render this organ the most sensible to external impressions. BILL AND TONGUE OF WILD DUCK (Anas boschas). In mammiferous animals, the membranous cuticle covers a corpus mucosum, generally of a soft viscid consistence, but in some few animals of this class, as the rhinoceros, armadillo, scaly ant-eater, &c., assuming the form of hard plates, like those of the crocodile and alligator. It is of the corpus mucosum, also, that are constituted, in some few, as the duck-billed animal, a perfect bill; and, in the greater number, the hair, fur, wool, bristles, quills, &c., with some one or other of which their bodies are covered; as well as the horns, claws, hoofs, &c., with which many of them are furnished. CONSCIOUSNESS SENSATION. 159 The cutis, lying under this, is, in all, the organ of touch; which is most acute, in the duck-billed animal, upon the bill; in the carnivorous tribes, at the root of the whiskers; in those with movable snouts, as the mole, hog and elephant, upon that organ; in the bat, upon the membrane between their fingers, commonly called their wings; and in most of the Glires, as the squirrel, as well as in apes and other animals of this description, at the tips of the fingers; since it is in these organs respectively that the papillæ are most abundant. It is unnecessary to point out how admirably this corresponds with the habits of each of these animals; and the delicacy of touch which some of them enjoy in the organs in question is wonderfulelephant, for example, being able to distinguish, by the tip of its trunk, between the most minute objects, and a bat being capable, though deprived of the use of its eyes and ears, to direct its rapid flight through the most intricate places, the touch alone of its membranous wings sufficiently apprising it of the contiguity of objects, and thus enabling it to avoid them. an Consciousness. The animal functions, or functions of relation, are currently spoken of as the functions on which consciousness peculiarly attends. The states of consciousness are the various states of animal being in which the sense of existence is present. Thus every exercise of mind in man is properly described as a state of consciousness. All his sensations, emotions, appetites, and desires, are so many states of his consciousness; since the feeling of existence is an essential element in all these several affections. The exercise of locomotion, in obedience to volition, is a state of consciousness; and even involuntary acts, such as yawning, sighing, hysteric laughing, and the like, come under the head of conscious acts, or acts into which, as an element, the sense of existence enters. Hence, it may be inferred, that, in the lower animals, acts of pure instinct, altogether independent of anything like volition, are often states of consciousness. Thus man's animal existence is made up of a long succession of states of consciousness, scarcely altogether interrupted even during sleep. The analysis and methodical arrangement of such states of consciousness constitute the proper business of the philosophy of the human mind. Of locomotion and the senses of animals we have already briefly spoken; and, for the present, a few words must suffice on sensation, emotion, reason, instinct, and thought. Sensation is a mental feeling, or state of consciousness, to which, however, certain corporéal preliminary conditions are essential. When the point of a needle makes the slightest puncture at the surface of the skin, a sensation takes place. The feeling of pain combined, if one so may speak, with a sense of existence, constitutes this sensation, distinctly entitled to be termed a state of conscious 160 SENSATION THE LINK BETWEEN MIND AND MATTER. ness. But there is also another element in such a sensation, which does not manifestly enter into every state of consciousness. That other element is, that the consciousness has a local seat; that the consciousness of pain is felt to exist at the point where the needle has pierced the skin. But anatomy quickly teaches us that the sensible point which the needle touches, is not the independent, although the manifested seat of sensation. It is found, that such a point of the surface of the body only remains sensible on condition that nervous filaments extend to it from the nervous centre, that is, from the brain or spinal marrow; that such filaments are entire and unbroken; and further, if they be divided, compressed, or otherwise seriously injured, that a needle may be thrust into the part without the production of any mental feeling whatever. In short, it is discovered by a little investigation, that when an impression, such as that made by a needle, affects the extremity of a nervous filament, a corresponding change occurs in the point of the brain, or spinal marrow, to which that nervous filament extends; and that this change in the nervous centre fails to occur, unless the nervous filament concerned be entire in its whole extent. The singularity here to be observed, is, that although the point in the nervous centre is plainly that on which the mental feeling depends, yet that that mental feeling is not felt to have any local existence, except at the extremity of the nervous filament touched by the needle. Thus the seat of sensation, the local seat of the state of consciousness, which constitutes a sensation, is always in the organ, or part of the body, where the nervous filaments concerned terminate. It is quite true, as Epicharmus sung: "Mind it seeth, mind it heareth- nevertheless, the local seat of sensations is in the skin, the membrane of the nostrils, the membrane of the tongue, the labyrinth of the ear, the retina of the eye, and finally, in the locomotive organs in general, when brought into action. The mind has, indeed, no local seat. It would be absurd to speak of a spiritual essence as having parts, or being in connexion with space; but, nevertheless, it is quite certain that in sensation the mind manifests itself in what are termed the organs of sensation. Here it is, then, in the skin and the other organs of sensation, that the confines of mind-so to speak-and the confines of matter meet. Nor is it erroneous to say that it is in sensation that mind communicates with matter. This view leaves the spirituality of the sentient principle wholly untouched. For, as Sir William Hamilton remarks (REID's Works, p. 862), "the connexion of an unextended with an extended substance, is equally incomprehensible, whether |