the external parts, as to bring confusion on the sensations, and trains of ideas, and convulsions on the muscular system. And that these effects are produced by a local influence on the stomach, in the manner proposed concerning opiates, appears, because they cease, or abate much, soon after the narcotic is ejected by vomiting; also because whipping a dog, after he has taken the nux vomica, contributes to obviate its ill effects. Wines, and grateful aliments, dispose to sleep, partly by their immediate effects on the stomach, partly by their effects after they are absorbed. But the degree not being so great as in opiates, it may more easily be overcome by a variety of common or vigorous impressions; in which case the vivid vibrations, excited by the wine or aliment, will illuminate all the impressions, and add strength to all the motions. The same thing is observed of opiates, in those who take them frequently.
Sixthly, Chylification, sanguification, nutrition, and growth, seem to proceed best during sleep. This may be conjectured from the sleepiness of all animals after eating, since sleep and chylification, &c. must here concur; and from the almost constant sleep of new-born children, above taken notice of, since nature seems chiefly intent on the due performance of these functions, for some time after birth. Now the doctrine of vibrations may be made to illustrate these points, in some measure. For since respiration becomes strong and convulsive at the instant of going to sleep, it will renew and increase the vibrations excited in the nerves of the stomach and bowels by their contents, which we must suppose to have languished before, in the same manner as those which subsisted in the external senses. The organs of digestion therefore, as well as those of respiration, are in a state of vigilance, and are intent upon the performance of their proper functions, while the other parts are in a state of sleep and inaction, and recruiting, in order to perform their functions in a due manner, upon a return of vigilance. And this holds most particularly in respect of the medullary substance of the brain, spinal marrow, and nerves, which, by the consent of all, is the chief instrument of nutrition and growth. Since the vibrations which take place in it during sleep are languid, it will then be filled and recruited, and consequently fitted for nutrition and growth; which will be farther favoured by the concurrence of a complete chylification and sanguification, at the same time.
The increased convulsive respiration, and increased force of the heart, which take place at the instant of going to sleep, and continue frequently during sleep, may perhaps be thus accounted for, agreeably to the doctrine of vibrations. When vivid vibrations cease in the external senses, and regions of the brain belonging to them, also in the muscles of the limbs, and parts of the spinal marrow corresponding thereto, this abatement of vibrations must either extend to the whole medullary substance, which seems to be the case in the night-mare; or if the
