Page:The System of Nature.djvu/136

 that of feeling. Nevertheless, if we wish to define to ourselves a clear and precise idea of it, we shall find that feeling is a particular manner of being moved&mdash;a mode of receiving an impulse peculiar to certain organs of animated bodies, which is occasioned by the presence of a material object that acts upon these organs, and transmit the impulse or shock to the brain.

Man only feels by the aid of nerves dispersed through his body; which is itself, to speak correctly, nothing more than a great nerve; or may be said to resemble a large tree, of which the branches experience the action of the root, communicated through the trunk. In man the nerves unite and lose themselves in the brain; that intestine is the true seat of feeling: like the spider in the centre of his web, it is quickly warned of all the changes that happen to the body, even at the extremities to which it sends its filaments and branches. Experience enables us to ascertain, that man ceases to feel in those parts of his body of which the communication with the brain is intercepted; he feels very little, or not at all, whenever this organ is itself deranged or affected in too lively a manner. A proof of this is afforded in the transactions of the Royal Academy of Sciences at Paris: they inform us of a man who had his scull taken off, in the room of which his brain was recovered with skin; in proportion as a pressure was made by the hand on his brain, the man fell into a kind of insensibility, which deprived him of all feeling. BARTOLIN says, the brain of a man is twice as big as that of an ox. This observation had been already made by ARISTOTLE. In the dead body of an idiot dissected by WILLIS, the brain was found smaller than