conditions as existing in other antecedent and concomitant thoughts and feelings. But of their conditions, as existing in the shape of antecedent or concomitant brain-processes, we have no knowledge worthy of being called science. Exner's declaration is almost as true to-day as it was several years ago, when he made it. "There is no science of cerebral physiology." If, then, it is necessary, laying aside all metaphysical postulating of deeper-lying (psychical) entities, in order to render psychology a natural science, that we should scientifically know the cerebral conditions of our thoughts and feelings, and should bring under terms of exact formulae the relations of the latter to the former, we must at once abandon all pretence of scientific character for psychology. If cerebral psychology is the only scientific psychology, then there is no science of psychology.
There are two directions in which modern attempts make progress in laying the foundations of cerebral physiology. One of these is the localization of cerebral function, the other is so-called "nerve-physiology," as modified and complicated by the exceedingly obscure and complex molecular structure of the cerebral substance. The former of these investigations aims to discover where something takes place, which is somehow related to certain changes of our "thoughts and feelings"; — or rather, so far as yet appears, chiefly (perhaps exclusively) to changes in our sensory-motor mental life. The latter aims to describe precisely what it is that takes place, whenever a so-called "cerebral process" occurs in uniform relation to these changes of thoughts and feelings. One inquiry admits, in part, of experimental testing; it has made rapid and brilliant progress since the epoch-making experiments of Fritsch and Hitzig in 1870. The other inquiry — the investigation which, if it succeeded, would tell us, in terms of molecular science, the precise nature of brain-processes related to thoughts and feelings, and precisely how they change, if at all, in character, as the related thoughts and feelings change — is in a hopeless muddle still. Not all the physiologists in the world can say "in terms of molecular science," what is done by the sciatic nerve of a frog, with the gastro- -
