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THE POPULAR SCIENCE MONTHLY.

electrical work spent upon it. The latter result is alone to the point, as in the former the efficiency of the dynamo-machine enters as an element, as well as that of the storage-battery. On this showing the storage-battery does not seem to have reached a commercial stage, but that it will do so at no very remote time there is every warrant for believing, when we consider the large amount of attention there is now being given to the subject, and the rapidity with which electric appliances are at present passing out of the experimental into the industrial stage.

 


LITERARY NOTICES.
INTERNATIONAL SCIENTIFIC SERIES, No. XLI.

Diseases of Memory: An Essay in the Positive Psychology. By Th. Ribot, author of "Heredity: its Phenomena, Laws, Causes, and Consequences," "English Psychology," etc. Translated from the French by William Huntington Smith. D. Appleton & Co. Pp. 209. Price, $1.50.

From both a scientific and a practical point of view this monograph is among the most interesting and valuable that have appeared in the "International Series." It is an able statement of the latest knowledge on a subject which concerns almost every-body. "We can here only intimate the author's stand-point in the discussion.

Where are our thoughts when we are not thinking them? Not a ten-thousandth part of the great stock of mental acquisitions which a man possesses is ever in consciousness at any one time. And, of those which in our waking states are ever rapidly emerging and disappearing, only a very small portion are obedient to the will—they exist and are preserved independently of consciousness, and they come and go, to a large extent, by laws deeper than volition.

Where, then, is the great stock of our ideas when we arc not aware of them? The common, the pre-scientific answer is, they are in the mind, which is an abstract spiritual container, of which we only know that it is an immaterial essence. This mind is made up of faculties, and memory is one of these faculties, in which the intellectual contents are stored up until called for by voluntary thought. Hamilton speculated vaguely about "mental latency," but where the mental stock is kept was always regarded as a great mystery—in fact, an insoluble mystery which there was no use in working at, because all the mind that concerns us is the mind we know about. Mind was thus bounded by consciousness, and memory, or the recall of ideas, was considered purely as a matter of volition, while this faculty in all men was looked upon as very much the same thing. Dugald Stewart, for example, says of the memory, "that original disparities among men, in this respect, are by no means so immense as they seem to be at first view, and that much is to be ascribed to different habits of attention, and to difference of selection among the various objects and events presented to their curiosity."

But it is obvious enough that nothing can be done with the problem of mental disease under this view; and, if we are to inquire concerning "diseases of memory," the first thing is to ascertain what we have to deal with that is capable of being diseased. This, of course, is the corporeal part of our nature, and it implies at once that memory has its organic side. It is the nervous part that registers and conserves our psychical acquisitions, and accordingly Professor Ribot begins his work by the study of nervous structures, properties, and activities, and with the consideration of memory as a biological fact. Memory implies three things: first, an impression, and therefore an organism capable of receiving impressions. The various senses bring, and the nervous centers receive and record, these impressions. The centers, moreover, recombine, reassociate, and elaborate these impressions in the most complex ways. This implies, secondly, a conserving or retaining capacity of the nerve-centers, which answers to the notion of mental storing. Then there is, thirdly, the emergence of these impressions in thought, or conscious recollection. This deliverance in consciousness is a result which we might call incidental, and depends, of course, on the prior conditions of impressibility and conserva-