« PreviousContinue »
which, in the number of its species, so vastly outweighs all the other tribes taken together, the nourishing juices are not carried through this circulation ; but on being absorbed by the pores of the intestines, are at once imparted to the whole spongy mass of the body: still, the access of air is indispensable, as in other ani- ? mals, and is effected through openings upon all points of the body, called tracheae, through wbich air or water is admitted.
In animals possessed of circulation, we detect no special arrangement or apparatus for depositing the solid particles of the body; the molecules are simply evolved from a minute subdivision of the last arterial branches. For the deposition of liquids, however, the extremity of those vessels containing the nutritive matter, expand over large surfaces, from which the liquid to be produced exhales; or the extremities of these vessels, before changing into veins, give rise to capillary vessels, which, interlacing with numerous blood-vessels, form secretory glands. In addition to these glands, there are others for the separation of certain liquids, which are ejected as superfluous, or are of some service to the animal; as, for example, the ink of the cuttle-fish, with which it discolors the water, in order to elude the pursuit of its enemies
. The production of a germ is involved in still greater mystery than the subject of assimilation. When detached, however, from the parent, it takes upon itself an independent existence. The change of forin through which it passes, from the time of assuming individual life, to the adult period, is always considerable, and sometimes so striking as to have been termed a metamorphosis
. The antennæ, wings, and legs, of the butterfly, are for a fixed period closely folded away in the skin of the unsightly caterpillar. The feet of the frog are enclosed in the skin of the tad-pole; and the tadpole, before becoming a perfect frog, loses its tail, mouth, and gills.
Of the important facts in animal physiology, just enumerated, Cuvier selects those relating to the functions of sensation and motion, as the grounds of his system ; observing, that these not only constitute the being an animal , but establish, in some manner,
the degree of its animality :-observation proving that the degree of development, and of complication of the animal functions, is in concordance with that of the organs of the vegetative functions. The heart, and the organs of circulation, are a species of center for the vegetative functions, as the brain and trunk of the nervous system are for tbe animal functions. The two systems diminish or disappear together. In animals of the inferior tribes
, where there are no visible nerves, there are no distinct fibers, and the organs of digestion consist of simple cavities in a homogeneous mass.
Taking, therefore, the correspondence of the general fornus, which results from the arrangement of the motive organs, the distribution of the nervous masses, and the energy of the circulating
stem, as a basis for the primary classes, we have the four
of VERTEBRATED, MOLLUSCOUS, ARTICULATED, and LIATED ANIMALS. In eertebrated animals, the brain, and the principal truok of the Tvous system, are enclosed in a bony envelop, which forms the all and vertebræ. To the sides of the vertebral column are atched the ribs and bones of the members that form the frameork of the body.
Animals of this form have red blood, a musilar beart, a mouth with two horizontal jaws, and never more van four limbs: distinct organs of sight, of hearing, of taste, and neil
, are placed in the cavities of the face. To this group beags man, and the animals that resemble bim most, even down to ne lowest of the fishes. In molluscous animals, there is no skelea; the muscles are only attached to the skin, which forms a soft evelop, in numerous species producing stony coverings, called sells, the position and extent of which correspond to those of the tucous body. The nervous system is composed of many distinct aeses, united by threads; the principal of these are placed near de Esophagus, and have received the name of the brain. Aniials of this group possess only the senses of taste and sight. be system of circulation is, however, complete, and there are articular organs for respiration. The organs of digestion and ecretion are nearly as complicated as those of the first mentioned Toup. The cuttle-fish, and the immense tribe of shell-fish, fall vithin this plan of organization. In articulated animals, as in in&cts
, worms, etc., the nervous system consists of two long cords, anging along the body, and swelling out at intervals into ganglions, of knots. The envelop of the trunk is divided by transverse folds into a certain number of rings, the coverings of which are sometroes hard, and sometimes soft, the muscles being attached to them beneath. In animals of this class is first observed the passage, from circulation in a vascular system, to nutrition by imbobition, and a corresponding passage from respiration in circumscribed organs, to that in air-vessels spread over the whole body. The organs of taste and sight are the most distinct in the articulazed animals. The jaws are always lateral. The radiated animals comprise the zoophytes. In these, the organs of sense and motion are placed circularly round a center. They approach in substance the bomogeneity of plants, exhibiting no distinct nervous system, nor organs of particular senses. In some of these, we scarcely perceive any traces of circulation ; their organs of respiration are almost always on the surface of the body : in the greater number, the whole intestine is simply a cavity with a single opening; and in the lowest families, the bodies consist of a mere pulp, apparently destitute of mobility and sensation. It would be a grateful task, to give a sketch of Cuvier's account of the living principle and its effects,-of sensatio muscular motion; as these topics were among the introd views on physiology, so luminously presented in the work consideration : but we must content ourselves simply with stract of his remarks, on the intellectual faculties and insti animals, before passing to a notice of the classes of the ver
The impression of external objects on the mind, in the p tion of a sensation or images, in the view of Cuvier, is an in trable mystery. Nor can materialism be summoned to our this dilemma, since philosophy is incapable of furnishing any proof of the existence of matter. An invariable law of ou derstanding, however, forces us to refer the objects exciting ou sations, to something out of the mind, to which we give the pa matter. The naturalist is nevertheless bound to examinei appear to be the material conditions of sensation,—to traced terior operations of the mind, and to ascertain how far they subject to conditions of perfection dependent on the organiz of each species, or on the momentary state of each individual b
In order that external objects may be perceived, it is nece that there should be an uninterrupted nervous communica between the organs of sense and the central masses of medullary system ; for it is only the modifications of these ma that are perceived by the mind. There may be real sensati without any external organ being affected, and which originate ther in the nerves or the brain : such are dreams, visions, certain accidental sensations. In the words of Cuvier himself
• The modifications experienced by the medullary masses, leave pressions there which are re-produced, and thus recall to the mind ir ges and ideas ; this is memory, a corporeal faculty that varies gied! according to the health and age of the animal. Similar ideas, or sa as have been acquired at the same time, recall each other; this is association of ideas. The order, extent, and quickness, of this 25 ciation, constitute the perfection of memory. Every object preset itself to the memory, with all its qualities, or with all its accesso ideas. Intelligence has the power of separating these accessory ide of objects, and of combining those that are alike in several differe objects, under a general idea, the object of which no where real exists ; this is abstraction. Every sensation being more or le agreeable or disagreeable, experience and repeated essays soon shu what movements are required to procure the one and avoid the otber and with respect to this, the intelligence abstracts itself from the gen ral rules, to direct the will. An agreeable sensation being liable consequences that are not so, and vice versa, the subsequent sensation become associated with the idea of the primitive one, and modity th general rules framed by intelligence; this is prudence. From the af plication of these rules to general ideas, result certain formula, whic
terwards easily adapted to particular cases ; this is called rea
A lively remembrance of primitive and associated sensations, the impressions of pleasure or pain that belong to them, constiimagination. e privileged being, Man, has the faculty of associating his geneeas with particular images, more or less arbitrary, easily impressed the memory, and which serve to recall the general ideas they re
These associated images are styled signs; their assemblage anguage. When the language is composed of images that relate sense of hearing or of sounds, it is termed speech; and when ree to that of sight, hieroglyphics. Writing is a suite of images that es to the sense of sight, by which we represent the elementary ds, and by combining them, all the images relative to the sense of ag, of which speech is composed: it is therefore only a mediate ésentation of ideas. las faculty of representing general ideas by particular signs, or imaassociated with them, enables us to retain distinctly, and to rememwithout embarrassment, an immense number; and furnishes to the waing faculty and the imagination, innumerable materials, and to induals means of communication, which cause the whole species to teipate in the experience of each individual : so that no bounds seem pe placed to the acquisition of knowledge; it is the distinguishing nacter of human intelligence. Although with respect to the intellectual faculties, the most perfect imals are infinitely beneath man, it is certain that their intelligence Torus operations of the same kind. They move, in consequence of usations received, -are susceptible of durable affections, and acquire p experience a certain knowledge of things, by which they are govbed, independently of actual pain or pleasure, and by the simple resight of consequences. When domesticated, they feel their subdoration,—know that the being who punishes may refrain from doing oif he will; and when sensible of having done wrong, or behold him ngry, they assume a suppliant and deprecating air. In the society of mn, they become either corrupted or improved, and are susceptible of mulation and jealousy: they have among themselves a natural language, which, it is true, is merely the expression of their momentary Pusations ; but man teaches them to understand another, much more complicated, by which he makes known to them his will, and causes them to execute it.
To sum up all, we perceive in the higher animals a certain degree of feason, with all its consequences, good and bad, and which appears to be about the same as that of children, ere they have learned to speak. The lower we descend from man, the weaker these faculties become ; and at the bottom of the scale, we find them reduced to signs (at times equivocal
) of sensibility, that is, to some few slight movements to escape from pain. Between these two extremes, the degrees are infinite.
In a great number of animals, however, there exists another kind of intelligence, called instinct. This induces them to certain actions necessary to the preservation of the species, but very often altogether foreign to the apparent wants of the individual ; often also very complicated,
and which, if attributed to intelligence, would suppose a foresig knowledge in the species that perform them, infinitely superior to can possibly be granted. These actions, the result of instinct, the effects of imitation ; for very frequently the individuals who them have never seen them performed by others: they are not p tioned to ordinary intelligence, but become more singular, more more disinterested, in proportion as the animals belong to less el classes, and in all the rest of their actions are more dull and They are so entirely the property of the species, that all its indir perform them in the same way; without ever improving them a pa
The working bees, for instance, have always constructed veryi nious edifices, agreeably to the rules of the highest geometry, ant tined to lodge a posterity not even their own. The solitary bee the wasp also, form highly complicated nests, in which to deposit eggs. From this egg comes a worm, which has never seen its pe which is ignorant of the structure of the prison in which it is con but which, once metamorphosed, constructs another precisely simili
The only method of obtaining a clear idea of instinct, is by admi the existence of innate and perpetual images or sensations in the sorium, which cause the animal to act, in the same way as ordina accidental sensations usually do. It is a kind of perpetual visit dream, that always pursues it ; and it may be considered, in all that relation to its instinct, as a kind of somnambulism. "*
VERTEBRATED ANIMALS constitute, of course, the most import group in the animal races. Great strength and precision of tion is secured to them, by means of the movable pieces wh unite to form the frame-work of their bodies; and the general lidity of these materials, permits them to attain greater dimensi than the animals of the other divisions. The concentration of i nervous mass, and the superior volume of the brain, also rend their sensations more energetic and durable, and thus impart them higher degrees of intelligence.
To extend the brief enumeration of properties of vertebrate animals, adduced as the characteristic of this group, it may be a ded, that the body is composed of a head, a trunk, and limbs. Th head is formed of the skull,—the receptacle of the brain, and the face, in which the organs of sense are situated: The solid part of the trunk, are the spine and the ribs. The spine is made up o numerous bones, called vertebræ, moving upon each other; the firs of which supports the head, the other extremity frequently being prolonged beyond the lower limbs. The vertebræ are perforated so as to form a long tube throughout the spine, in which is lodged the root-like prolongation of the brain, called the spinal marrow. The ribs are semi-circular bones, which protect the sides of the cavity of the body. One or both pair of limbs may be wanting ; the fore limbs being converted into hands or feet, legs or fins, the
Animal Kingdom, translated by H. M'Murtrie. New-York, 1831. p. 35, et seq.