Page:Mind (Old Series) Volume 12.djvu/131

 118 CEITICAL NOTICES ! from Switzerland two years before the dream. Just as the con- sideration of the illusory character of the dream led our author to the wide philosophical question of the criterion of knowledge, so the psychological analysis of his dream conducts him to the gene- ral problem of memory. The reproduction with perfect clearness of a name, the origin of which was wholly forgotten, suggests that no impression is entirely lost. The fact of a uniform conser- vation of psychical impressions naturally connects itself with the law of conservation of energy, and the author does not shrink from discussing the nature and grounds of this far-reaching prin- ciple. He thinks that the doctrine of the transformation of energy is commonly taken to mean that the actual order of cosmic events is capable of being repeated, and he takes some pains to disprove this supposition. The whole progress of things is towards an equilibrium in which no further change is possible. Every transformation of a force leads to a partial fixation of what was once free. The transformable gives place to the intransformable. The conservation by memory of the traces of past impressions is a special illustration of these vast all-embracing laws. The assimilation by the brain of external impressions may be regarded as a fixation of external forces. Just as the crust of the earth indicates by the succession of its strata all the changes in the history of our planet, so, according to Prof. Delboeuf, the organism is constituted by layers which represent the past actions of itself and its ancestors. He resolves these into a central nucleus consisting of the ensemble of hereditary elements, instincts, dispo- sitions, &c., and a region or " depot of formation," the result of its assimilative faculty, and consisting of an uninterrupted series of layers representing its daily acquisitions. This idea of a central nucleus and enveloping layers is, the author tells us, merely a metaphor for helping us to conceive the fact that the individual is composed of what he receives from his ancestors and of what he himself acquires. He pursues his biological speculations at some length, discussing the " mysterious and fundamental general functions " of nutrition and of generation and of their relations one to another. There is much here that is suggestive, but much also that seems too figurative to be of any considerable scien- tific value. It must be confessed further that in some cases, as, for example, when he seeks to give a new definition to 'centre' and 'periphery,' his meaning is not as clear as it might be ; the reader feels that the author, in his bold and brilliant career over the theory of the origin and end of all things, fails to do justice to many of the topics which he touches. He does, no doubt, apologise for his digressions by telling us he is writing not a treatise but an essay ; but even an essay ought perhaps to have the unity which only a well-defined subject can impart, and what one rather misses in Prof. Delboeufs volume is an attempt to define the limits of his subject. When at last he does recur, at the close of this second section of his work, to the proper psychological problem of