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not be an organ of taste or smell as well as of touch; and there are some naturalists that in like manner regard the cirrous filaments or antennules attached to the mouths of insects as organs of taste and touch equally. Taste in the more perfect animals resides jointly in the papillæ of the tongue and the palate; but I have already had occasion to observe that it may exist, and in full perfection, in the palate alone, since it has been found so in persons who have completely lost the tongue from external force or disease.

CLASS IV.

I. Nature

of the brain, its ramifications and

substitutes. Seat of

taste in the

higher

classes.

seat of
smell where

In animals that possess the organ of nostrils this is Nostrils the always the seat of smell; and in many quadrupeds, most birds, and perhaps most fishes, it is a sense far more acute they exist. than in man, and that which is chiefly confided in. For the most part it resides in the nerves distributed over a mucous membrane that lines the interior of the bones of the nostrils, and which is called the Schneiderian membrane, in honour of M. Schneider a celebrated anatomist, who first accurately described it. Generally speaking it will be found that the acuteness of smell bears a proportion in all animals to the extent of surface which this membrane displays; and hence in the dog, and cattle tribes, as well as in several others, it possesses a variety of folds or convolutions, and in birds is continued to the utmost points of the nostrils, which in different kinds open in very different parts of the mandible.

Differs in

intensity in "different

The frontal sinuses, which are lined with this delicate membrane, are larger in the elephant than in any other quadruped, and in this animal the sense is also continued through the flexible organ of its proboscis. In the pig the smelling organ is also very extensive; and in most of the mammals possessing proper horns it ascends as high as the processes of the frontal bone from which the

horns issue.

animals, and

why.

ous tribes

It is not known that the cetaceous tribes possess any Whether organ of smell; their blowing-holes are generally re- the cetacegarded as such; but the point has been by no means possess fully established. We are in the same uncertainty in respect to amphibials and worms; the sense is suspected

VOL. IV.

smell?

Whether amphibials

or worms.

.

CLASS IV. to exist in all the former, and in several of the latter,

I. Nature

of the

brain, its ramifications and

substitutes.

Possest by fishes, and very acutely.

Possest
by insects,
but the

organ not
known.

Hearing, its general

organ

the

ear, though not always.

especially in the cuttle-fish; but no distinct organ has hitherto been traced out satisfactorily.

In fishes there is no doubt; the olfactory nerves are very obviously distributed on an olfactory membrane, and in several instances the snouts are double, and consequently the nostrils quadruple, a pair for each snout. This powerful inlet of pleasure to fishes often proves fatal to them from its very perfection; for several kinds are so strongly allured by the odour of marjorum, assafoetida and other aromas, that by smearing the hand over with these substances, and immersing it in the water, they will often flock towards the fingers, and in their intoxication of delight may easily be laid hold of: and hence the angler frequently overspreads his baits with the same substances, and thus arms himself with a double decoy.

There can be no doubt of the existence of the same sense in insects, for they possess a very obvious power of distinguishing the odorous properties of bodies even at a considerable distance beyond the range of their vision: but the organ in which this sense resides has not been satisfactorily pointed out; Reimar supposes it to exist in their stigmata, and Knoch in their anterior pair of feelers. The general organ of HEARING is the ear, but not always so; for in most of those who hear by the Eustachian tube only, it is the mouth; in the whale tribes it is the nostrils or blow-hole. It is so, however, in all the more perfect animals, which usually for this purpose possess two distinct entrances into the organ, a larger and external surrounded by a lobe; and a smaller and internal opening into the mouth. It is this last which is denomiEustachian nated the Eustachian tube. The shape of the lobe is seldom found even in mammals similar to that in man, excepting among the monkey and the porcupine tribes. In many kinds there is neither external lobe nor external passage. Thus in the frog, and most amphibious animals, the only entrance is the internal or that from the mouth; and in the cetaceous tribes the only effective entrance is probably the same kind; for, though these may be said to

tube.

External organ varies in different kinds.

I. Nature of the

ramifications and

possess an external aperture, it is almost imperceptibly CLASS IV. minute. It is a curious fact that, among the serpents, the blind-worm or common harmless snake is the only species brain, its that appears to possess an aperture of either sort; the rest have a rudiment of the organ within, but we are not substitutes. acquainted with its being pervious to sound. Fishes are well known to possess a hearing organ, and the skate and shark have the rudiment of an external but like other fishes they seem chiefly to receive sound by Fishes hear, the internal tubule alone.

ear;

That insects in general hear is unquestionable, but it is highly questionable by what organ they obtain the sense of hearing. The antennas, and perhaps merely because we do not know their exact use, have been supposed by many naturalists to furnish the means; it appears fatal, however, to this opinion to observe, that spiders hear though they have no true antennas, and that other insects which possess them naturally seem to hear as correctly after they are cut off.

senses.

Serpents generally destitute of a hearing

organ.

and some have an ex

ternal organ. but

Insects hear,

the organ

uncertain.

Sight: its

organ

greatly

different

membrane,

The sense of VISION exhibits perhaps more variety in the different classes of animals than any of the external In man, and the greater number of quadrupeds varies in it is guarded by an upper and lower eye-lid; both of classes. which in man, but neither of which in most quadrupeds are terminated by the additional defence and ornament of cilia or eye-lashes. In the elephant, opossum, seal, catkind, and various other mammals, all birds, and all fishes we find a third eye-lid, or nictitating membrane as it is Nictitating usually called, arising from the internal angle of the eye its use. and capable of covering the pupil with a thin transparent veil either wholly or in part, and hence of defending the eyes from danger in their search after food. In the dog this membrane is narrow, in oxen and horses it will extend over half the eye-ball; in birds it will easily cover the whole; and it is by means of this veil, according to Cuvier, that the eagle is capable of looking directly against the noon-day sun. In fishes it is almost always upon the stretch, as in their uncertain element they are exposed to more dangers than any other animal. Ser

I. Nature

CLASS IV. pents have neither this nor any other eye-lid; nor any kind of external defence whatever but the common integument of the skin.

of the

brain, its ramifications and

substitutes. Largest proportioned eye. Smallest.

Iris.

Pupil : shape varies in different classes.

Position of

the eyes varies.

Spiders

multocu

late.

Eyes of sepia.

Polypes

and zoo

phytes perceive light, though apparently without eyes.

The largest eyes in proportion to the size of the animal belong to the bird tribes; and nearly the smallest to the whale; the smallest altogether to the shrew and mole; in the latter of which the eye is not larger than a pin's head.

The iris, with but few exceptions, partakes of the colour of the hair, and is hence perpetually varying in different species of the same genus. The pupil exhibits a very considerable, though not an equal, variety in its shape. In man it is circular; in the lion, tiger, and indeed all the cat kind, it is oblong; transverse in the horse and in ruminating animals; and heart-shaped in the dolphin.

In man, and the monkey tribes, the eyes are placed directly under the forehead; in other mammals, birds, and reptiles more or less laterally; in some fishes as the genus pleuronectes, including the turbot and flounder tribes, both eyes are placed on the same side of the head; in the snail they are situated on its horns, if the black points on the extremities of the horns of this worm be real eyes, of which, however, there is some doubt; in spiders the eyes are distributed over different parts of the body, and in different arrangements, usually eight in number, and never less than six. The eyes of the sepia have lately been detected by M. Cuvier; their construction is very beautiful, and nearly as complicated as that of vertebrated animals*. Polypes and several other zoophytes appear sensible of the presence of light, and yet have no eyes; as the nostrils are not in every animal necessary to the sense of smell; the tongue to that of taste, or the ears to that of sound. A distinct organ is not always requisite for a distinct sense. In man himself we have already seen this in regard to the sense of touch, which exists

Le Règne Animale distribué d'apres son Organization, 4 Tomes. 8vo. Paris, 1817.

CLASS IV.

I. Nature

of the brain, its tions and substitutes. The sense probably general but dull as

ramifica

both locally and generally; the distinct organ of touch is the tips of the tongue and of the fingers, but the feeling is also diffused, though in a subordinate and less precise degree, over every part of the body. It is possible, therefore, in animals that appear endowed with particular senses without particular organs for their residence, that these senses are diffused, like that of touch, over the surface generally; though there can be no doubt that, for want of such appropriate organs, they must be less acute general and precise than in animals that possess them.

that of

touch.

Whether any tribe other senses

possesses

com

than the

mon. Suspected

in the bat.

Whether

Whether there be any other than the five senses common to man and the higher classes of animals may be reasonably doubted, but we occasionally meet with peculiarities of sensation that can hardly be resolved into any of them. Thus the bat appears to be sensible of the presence of external objects and obstructions that are neither seen, smelt, heard, touched, or tasted: for it will cautiously avoid them when all the senses are purposely closed up. And hence many naturalists have ascribed a sixth sense to this animal. It is equally difficult by any in migraof the known senses of fishes or of birds to account for the tory birds accuracy with which their migratory tribes are capable of or fishes? steering their annual course through the depths of the ocean or the trackless regions of the atmosphere, so as to arrive at a given season on a given coast or a given climate, with the precision of the expertest mariner. Whilst with respect to mankind themselves we sometimes meet with persons who are so peculiarly affected by the presence of a particular object that is neither seen, smelt, tasted, heard, or touched as not only to be conscious of its presence, but to be in great distress till it is removed. The presence of a cat not unfrequently produces such an effect; and the author has himself been a witness of the most decisive proofs of this in several instances. It is possible that the peculiar sense may, in such cases, result from a preternatural modification in some of the branches of the olfactory nerve, which may render them capable of being stimulated in a new and peculiar manner; but the individuals thus affected are no

Whether

even in

mari ?

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