Page:Mind (New Series) Volume 15.djvu/69

 PRESENTATION AND REPRESENTATION. 55 In such a piece of matter as the nervous system of man, my special reaction in any part, however small it be, to any impulse whatever, must disturb an immense number of re- itions which can only be restored by a very special set of physical impulses bearing inherent relations to one another of enormous complexity ; and the probability of the appear- ance of such a special set of physical impulses is evidently so exceedingly small, that it may well be held that no such appearance is possible. We of course must not overlook the fact, however, that the most marked distinction between living matter and non- living matter is this : that while on the one hand complex inorganic masses after reaction to a physical impulse da not often even appear to regain their original form, on the other hand organic masses after reaction to a physical impulse do seem to regain the form which appeared before the reaction,, and this by processes which seem to be inherent in tnem- selves, and not determined by the occurrence of new impulses in their environment. But in consideration of the facts above presented we find it very difficult to see how this re- covery of its first condition can really be entirely complete, and we are led to suspect that, although the nature of living latter is such that it of itself tends to regain after a reaction /hat appears to be something very close to its condition as it sxisted before the reaction, nevertheless this appearance of identity of condition must necessarily be due to an illusion letermined by our weakness of observation. Evidence that recovery of its condition after a reaction is never exactly complete is given in the fact that living matter, more or less gradually, but none the less surely, changes in form and in structure ; as is seen in the fact that it grows old and finally dies. We are led therefore to assume that some slight, even if it be unobservable, change is made in the structure of each bit of living matter, and in the relation of its parts, in con- nexion with each of its reactions ; so that in reality after each reaction it no longer remains the same bit of living matter, capable of becoming what it was before its reaction ; but rather that after each reaction, however slight, it becomes a bit of living matter of a new form. In the complex nervous system of man we have innumer- able bits of living matter all closely related, and we are therefore compelled to accept the view that the form and structure of the parts, and of the whole, of the nervous system must change with each reaction. 1 In the organic systems of the highest grade of complexity this change the organism as a whole is masked probably by a replacement of cell