b. ANIMAL SENSES.
2475. It now only remains for us to consider the motor and the sensitive system proper upon their highest stage of development. The motor system, when represented in the nervous system, is a peculiar organ of sensation, as is likewise the nervous system itself upon attaining its highest state of development.
4. Osseo-Muscular Sense.
2476. The lowest condition of the motor system is the limbs, which represent no peculiar sense, but only the sense of feeling refined or set in motion. This motor system ascends into the head, and there no longer exercises its motive powers in prehension, progression, &c., but solely unto sensation. Now, a system, which converts its function into that of sensation, is a sense.
2477. The sensorial organ, which simply through motion, or a resistance presented to that of the atoms, produces sensation, or wherein the motion as such is felt, is the Ear.
2478. The ear is none other than the ultimate development of the bone and muscle, when they are brought under the direct dominion of the nerves.
2479. The auditory ossicles are the limbs subtilized or refined in character. They have joints, are provided with muscles, and move exactly like the limbs. It may be said; that the stapes is the scapula, the incus the humerus, the malleus the fore arm, and the concha with its cartilages, the hand with its digits.
2480. The ear, like the bulk of the limbs, has originated from branchiæ. In Fishes, the auditory ossicles have degenerated into the branchial opercula.
2481. The ear-trumpet (or Eustachian tube), which opens into the mouth, is the internal branchial aperture.
2482. The motor system, however, belongs to the trunk, whose viscera are repeated also in the ear, or in a cavity which has been called its labyrinth. The three semicircular canals appear to correspond to the intestine, the cochlea to the trachea.