Page:Physiological Researches upon Life and Death.djvu/30

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Two perfectly similar globes receive the impression of the light. Sound and odours have each also their double analogous organ. A single membrane is the seat of savours, but in it the median line is manifest; and each division marked by it resembles that of the opposite side. The skin does not always present to us visible traces of this line, but it may be supposed present throughout. Nature, in forgetting, if it may be thus said, to draw it, has placed from space to space, striking indications of its course. The fissures at the extremities of the nose and chin, and in the middle of the lips, the umbilicus, the raphe of the perinæum, the projections of the spinous apophyses, and the middle hollow in the posterior part of the neck form the principal points of these indications.

The nerves which transmit the impression made by sounds, such as the optic, the acoustic, the lingual and olfactory are evidently assembled in symmetrical pairs.

The brain, the organ upon which the impression is received, is remarkable for its regular form; its pairs resemble each other on every side, such as the bed of the optic nerves, the corpora striata, the hippocampi, and the corpora fimbriata. Those parts not in pairs are all symmetrically divided by the median line, of which several afford visible traces, as the corpus callosus, the fornix, tuber annulare, &c.

The nerves which transmit the volitions of the brain to the agents of locomotion and voice, the locomotive organs formed in a great measure from the muscular and osseous systems, the larynx and its accessories, the double agents