It was an English physiologist, Charles Bell, who solved this problem by showing that the most important nerves of the face, with the exception of the special sensory nerves, are confined to two. If one of these nerves, called the trigeminal, be cut through, every trace of sensibility immediately disappears from the corresponding side of the face; if the other, the facial nerve, be severed, sensibility remains, but the face completely loses the power of movement, there is no longer any contraction of the muscles or change of expression in the face. I quote Charles Bell’s own words, since these two simple experiments still form the base of the physiology of the nervous system. 'If we cut the division of the fifth nerve which goes to the lips of an ass, we deprive the lips of sensibility; so when the animal presses the lips to the ground, and against the oats lying there, it does not feel them, and consequently there is no effort made to gather them. If, on the other hand, we cut the seventh nerve where it goes to the lips, the animal feels the oats, but it can make no effort to gather them, the power of muscular motion being cut off by the division of the nerve.’[4] [4] Ch. Bell: _Anatomy and Physiology of the Human Body_, v. ii., p. 394. London, 1826. The same takes place in the hand, the legs, and in all other parts of the body, which, according as the one or the other set of nerves is injured, feel but cannot move, or move and do not feel. In the ordinary circumstances of life no one becomes aware of these two fundamental properties of the nervous system, or at least we do not reflect that there are two distinct apparatus: the nerves which make us feel, and the nerves which cause movement. The intimate connection between these in the nerve centres and at the surface of the body renders special methods necessary to separate them, and allow them to act independently of each other. Claude Bernard, the greatest of French physiologists, and one of the most agreeable and successful authors who have ever popularised science, showed how these two elements may be dissociated by introducing certain poisons into the blood, which kill the finest ramifications of the nerves in the most inaccessible parts of the organism.