Excessive fits of anger and fear are also found often to hurry persons into madness.
In dissections after madness the brain is often found dry, and the blood-vessels much distended; which are arguments, that violent vibrations took place in the internal parts of the brain, the peculiar residence of ideas and passions; and that it was much compressed, so as to obstruct the natural course of association.
As in mad persons the vibrations in the internal parts of the brain are preternaturally increased, so they are defective in the external organs, in the glands, &c. Hence maniacs eat little, are costive, make little water, and take scarce any notice of external impressions. The violence of the ideas and passions may give them great muscular strength upon particular occasions, when the violent vibrations descend from the internal parts of the brain into the muscles, according to former associations of these with the voluntary motions (the same increase of vibrations in the internal parts of the brain, which hinders the ascending vibrations of sensation, augmenting the descending ones of motion). But maniacs are often very sluggish, as well as insensible, from the great prevalence of the ideal vibrations; just as persons in a state of deep attention are. An accurate history of the several kinds of madness from those physicians, who are much conversant with this distemper, is greatly wanted, and it would probably receive considerable light from this theory.
Religious considerations are the best preservative in hereditary or other tendencies to madness; as being the only sure means of restraining violent passions, at the same time that they afford a constant indefinite hope, mixed with a filial awe and fear; which things are eminently qualified to keep up a steadiness and sobriety of mind, and to incite us to such a course of action, as adds incessantly to the hope, and diminishes the fear. However, bodily labour, with a variety of mental occupations, and a considerable abstemiousness in the quantity and quality of diet, ought always to be joined.
Section VII
THE INTELLECTUAL FACULTIES OF BRUTES.
If the doctrines of vibrations and association be found sufficient to solve the phænomena of sensation, motion, ideas, and
