CHAPTEK III. ON SOME GENERAL CONDITIONS OF BRAIN-ACTIVITY. The elementary properties of nerve-tissue on which, the brain-functions depend are far from being satisfactorily made out. The scheme that suggests itself in the first in- stance to the mind, because it is so obvious, is certainly false : I mean the notion that each cell stands for an idea or part of an idea, and that the ideas are associated or 'bound into bundles' (to use a phrase of Locke's) by the fibres. If we make a symbolic diagram on a blackboard, of the laws of association between ideas, we are inevitably led to draw circles, or closed figures of some kind, and to connect them by lines. When we hear that the nerve-cen- tres contain cells which send off fibres, we say that Nature has realized our diagram for us, and that the mechanical substratum of thought is plain. In some way, it is true, our diagram must be realized in the brain ; but surely in no such visible and palpable way as we at first suppose.* An enormous number of the cellular bodies in the hemispheres are fibreless. Where fibres are sent off they soon divide into untraceable ramifications ; and nowhere do we see a simple coarse anatomical connection, like a line on the black- board, between two cells. Too much anatomy has been found to order for theoretic purposes, even by the anat- omists ; and the popular-science notions of cells and fibres are almost wholly wide of the truth. Let us therefore rele- gate the subject of the intimate workings of the brain to
- I shall myself in later places indulge in much of this schematization.
The reader will understand once for all that it is symbolic; and that the use of it is hardly more than to show what a deep congruity there is between mental processes and mechanical processes of some kind, not necessarily of the exact kind portrayed. * 81
