Page:Mind (Old Series) Volume 11.djvu/467

 466 A. BAIN : (1) The varying sense of the massiveness of sensations,, spoken of by Mr. Ward under the new coinage " Extensity". An increase in the mass affects us differently from an in- crease in the intensity. Putting the finger alone into hot water and then the whole hand increases the mass of sensibility, and we are aware of the increase ; and in this difference we have the beginning, or basis of operations, of the notion of space. (2) The existence of Local Signs in different parts of the body, as suggested by Lotze, and elaborated by Wundt. That is to say, underneath the apparent identity of touches in different parts of the skin there are latent differences that operate in making us feel that repetition or plurality cannot be on the same spot. A word upon each of these hypotheses. The importance of massiveness, as going along with simultaneous plurality, may be readily admitted. A single contact on the tip of the finger proves nothing, a double contact essentially requires a change of spot, and a multiplicity of contacts is compatible only with that expansion of surface that is otherwise revealed by greater massiveness, the consequence of a wider contact. But I am inclined to think that the massiveness operates as a basis of plurality, and somehow in concurrence with that, and not from any suggestiveness in itself. The existence of distinguishable signs all over the body, even without conscious difference, has always seemed to me to be something of a paradox, notwithstanding their accept- ance by able psychologists. There is a remarkable sameness of quality in our tactile feelings on every part of the skin ; so much so that we scarcely ever in practice remark any difference except in their locality. When we are put to it, we must admit that there are anatomical grounds for variety, as Mr. Ward points out : the difference of the underlying parts in one place bone, in another tendon, in a third fatty tissue should make a qualitative difference of sensation ; and by attending to such differences we should know whether a contact is on a hard part or a soft, on the upper surface of the foot or the heel. But not to speak of the substantial sameness of the two sides of the body, there are large por- tions of the skin with identical subjacent parts ; and our sense of local differences would appear to be as good where the identity is most complete as where it is most wanting. Although, in this great question, it is right to begin with Touch, we must end with Sight ; for it is visible extension that is our standing mental representation of space. Now,. take the starry sky, where one star differs from another in