The tongue of most birds is so dry and rigid, that. we can scarcely suppose it an organ of taste. As for the tongues of the inferior classes, it is difficult to form any correct judgmet respecting their use ; and it is proba ble that in most of the inferior animals, the tongue is rather an organ of deglutition that of taste. See CHAP. III. Sect. ii.
The sense of smelling appears to be much more ex tensively diffused than that of tasting ; but the organs subservient to this sense can, in many classes, scarcely be ascertained with certainty.
We find that a great many of the mammalia, espe cially the tribes of weasels, bears, dogs and cats ; the elephant, the hedgehog, and the mole, possess this sense much more acutely than man ; and on examining their nose, we find that the structure of the ethmoid bone is much more complicated ; that its convolutions are much more numerous than in most other animals. Hence the pituitary membrane in these animals has a much greater extent of surface, and admits of a much great er number of nervous ramifications being distributed to that organ. The elephant seems peculiarly fitted for delicacy of smell ; for besides the trunk, the external perforations of which are evidently intended for nos trils, and which is abundantly supplied with nerves, its frontal sinuses are remarkably large and extensive.
In the cetacea, there is no ethmoid bone, and the nerves of the first pair, which are the nerves of smell in man and mammalia, are wanting.
The nostrils of the cetacea open in the corona] sur face of their heads, and answer a double purpose, viz. that of breathing air when this part of their heads is raised above the water, and that of throwing out, during expiration, the water which they received by their mouths. These nostrils in the cetacea are called blow• ing holes, and will be particularly described when we come to treat of the anatomy of these animals under CETOLOGY.
It appears that BIRDS are always provided with nostrils, though in some species, as the puffin, these so are small, and so situated in the margin of the bill, as to be easily overlooked. The olfactory nerves pass to the nose through the orbits.
In REPILES and SERPENTS, there are two cartila ginous eminences, which seem to be the principal or gans of smell, and the olfactory nerves are distributed in a manner similar to that NN hich takes place in birds'.
Many FISHES appear to have double nostrils on each side, and within there is found a membrane disposed in semicircular folds, and having the olfactory nerves dis tributed upon it.
The smelling organs of INSECTS are by no means ascertained, though we cannot doubt that they possess the faculty in a high degree. Some have supposed the antenna to be the olfactory organs ; but Cuvier thinks that the structure of these parts wholly disqualifies them for that office. Some have considered the anterior parts of the palpi as the smelling organs, and Blumenbach thinks this a more probable conjecture.
Most classes of animals appear to possess the faculty of hearing ; and in all the superior classes, including MAMMALIA, CETACEA, BIRDS, FISHES, REPTILES, and SERPENTS, the auditory organs are sufficiently apparent. INsEcTs can doubtless hear ; hut it is uncertain by what organs they exercise this faculty. Many of the CRUS TA CEA have very evident internal auditory organs, which have been described and figured by professor Scarpa. Some of the MoLLuscA, as the sepia, have something like an auditory organ ; but in all below these, this organ seems altogether wanting.
The mammalia alone possess external ears ; but in some of these, as in most of the seals, some species of trichrcus, (manati), the mole, and the ornithorynchus, or (platypus), these are wanting. In some species, as the ass, the fennte (canis zerda) and the long-eared bat, the external cars are remarkably large. In the quadrumana, and in the porcupine, the external ears nearly resemble those of man, except that the cells which correspond to the mastoid cells in the human subject, are larger, for ming in some a single bony cavity, in others numerous cells, divided by bony plates, giving to the cavity the ap pearance of the inside of a poppy head.
The cetacea have no external ear, and the opening of the auditory passage is extremely small. The bony part of the internal ear, is either completely separated from the rest of the skull, or very loosely connected with it. The cavity of the labyrinth and the little articulating bones, are remarkably small ; and in these animals the eustachian tube does not communicate with the fauces, but opens into the blowing hole, though it is provided with a valve that prevents the water from passing into the cavity of the car.