This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1788 edition. Excerpt: ... CHAP. II. Instinct. H E mechanical principles of action may, I think, be re- duced to two species, instincts and habits. By instinct, I mean a natural blind impulse to certain actions, without having any end in view, without deliberation, and very often without any conception of what we do. Thus a man breathes while he is alive, by the alternate contraction and relaxation of certain muscles, by which the chest, and of consequence the lungs, are contracted and dilated. There is no reason to think, that an infant new-born, knows* that breathing is necessary to life in its new state, that he knowi how it must be performed, or even that he has any thought or conception of that operation; yet he breathes as soon as he i& born with perfect regularity, as if he had been taught, and got the habit by long practice. By the same kind of principle, a new-born child, when its stomach is emptied, and nature has brought milk into the mother's breast, sucks and swallows its food as perfectly as if it. knew the principles of that operation, and had got the habit of working according to them Sucking and swallowing are very complex operations. Anatomists describe about thirty pairs of muscles that must be em"ployed in every draught. Of those muscles, every one must be served by its proper nerve, and can make no exertion but by some influence communicated by the nerve. The exertion of all those muscles and nerves is not simultaneous. They must succeed Chap. 11. Chap. H. succeed each other in a certain order, and their order is no less necessary than the exertion itself. This regular train of operations is carried on according to the nicest rules of art, by the infant, who has neither art, nor science, nor experience, nor habit. That the infant feels the...