tation of the stimulus ends by transforming perception into pain, no one will deny; it is none the less true that this change arises at a definite moment: why at this moment rather than at another? and what special reason brings about that a phenomenon of which I was at first only an indifferent spectator suddenly acquires for me a vital interest? Therefore, on this hypothesis I fail to see either why, at a given moment, a diminution of intensity in the phenomenon confers on it a right to extension and to an apparent independence; or why an increase of intensity should create, at one moment rather than at another, this new property, the source of positive action, which is called pain.
Let us return now to our hypothesis, and show that affection must, at a given moment, arise outReal significance of pain; it is a local, unavailing effort. of the image. We shall thus understand how it is that we pass from a perception which has extensity to an affection which is believed to be unextended. But some preliminary remarks on the real significance of pain are indispensable.
When a foreign body touches one of the prolongations of the amoeba, that prolongation is retracted; every part of the protoplasmic mass is equally able to receive a stimulation and to react against it; perception and movement being here blended in a single property,—contractility. But, as the organism grows more complex, there is a division of labour; functions
