become differentiated, and the anatomical elements thus determined forego their independence. In such an organism as our own, the nerve fibres termed sensory are exclusively empowered to transmit stimulation to a central region whence the vibration will be passed on to motor elements. It would seem then that they have abandoned individual action to take their share, as outposts, in the manœuvres of the whole body. But none the less they remain exposed, singly, to the same causes of destruction which threaten the organism as a whole; and while this organism is able to move, and thereby to escape a danger or to repair a loss, the sensitive element retains the relative immobility to which the division of labour condemns it. Thence arises pain, which, in our view, is nothing but the effort of the damaged element to set things right,—a kind of motor tendency in a sensory nerve. Every pain, then, must consist in an effort,—an effort which is doomed to be unavailing. Every pain is a local effort, and in its very isolation lies the cause of its impotence; because the organism, by reason of the solidarity of its parts, is able to move only as a whole. It is also because the effort is local that pain is entirely disproportioned to the danger incurred by the living being. The danger may be mortal and the pain slight; the pain may be unbearable (as in toothache) and the danger insignificant. There is then, there must be, a precise moment when pain intervenes: it is when the interested
