effects. Vibrations, propagated either along the skin, through the mouth and nose, or up to the brain, and thence along the eighth pair of nerves, or, which is most probable, both ways, to that very sensible part the stomach, may produce sickness and vomitings. And if the gall-duct be contracted from the same cause during the vomitings, a sudden jaundice will follow from the violence with which the gall is forced back into the blood by the action of vomiting. Joy, sorrow, fear, melancholy, may easily follow according to the respective natures of the poisons, because these, according to this theory, all arise from, and are attended by, corresponding vibrations in the white medullary substance of the brain. And a like account may be given of the aversion to black, and the delight in glaring objects, and strong colours. The corresponding nerves of different animals have probably a general resemblance to each other, just as the corresponding viscera and fluids have. And thus the poison of rabid animals may have a peculiar power of affecting the nerves of the fauces, and muscles of deglutition, so as to produce the hydrophobia. Cold bathing also, and music, whose immediate effects seem confined to the solids, to the exciting vibrations in them, may cure respectively in the bite of a mad dog, and of the tarantula.
However, what is here alleged is not at all to be so understood, as if the immediate effects of poisons upon the fluids were not also very considerable. In some cases they may be greater, in others less, than those exerted upon the solids. It seems probable, that the poison is communicated from the fluids immediately affected to those at a distance, chiefly by means of the serous vessels. For these, having numerous immediate communications with each other, will transmit it freely, and yet so as that all the neighbouring parts may be affected somewhat in proportion to their nearness to the seat of the injury, as they are found in fact to be; whereas, were the diffusion of the poison to be made by the circulation of the fluids alone, all the parts would have an equal chance. But the propagation of the poison along the solid capillaments of the nerves is also a principal reason why the neighbouring parts are more affected than the distant ones. The effects of inoculation bear a great resemblance to those of venomous bites and stings; and the same may be said of venereal and other infections.
Hitherto we have considered only the more vigorous sensations of feeling, such as may be called the pleasures and pains of this sense. We come now to the feeble and adiaphorous sensations. These are moisture, dryness, softness, with fluidity,
