Page:Mind (Old Series) Volume 9.djvu/486

474 MISCELLANEOUS. necessarily indirect or ' ejective,' we can never aim at any such precise classification of animal minds as we can of animal bodies. The most that we can ever hope to achieve is to indicate in the zoological scale where this or that faculty of mind first gives definite evidence of its appearance. And this is all that I have attempted to achieve. I regret that Mr. Whittaker has not alluded to my views on the origin of Memory as precedent to the association of ideas, and on the origin of Reason in the unconscious inferences of perception. I regret this because I had looked forward to the review of my book in MIND as the one which would probably have discussed these views. The Croonian Lectures were delivered in March of this year, at the Royal College of Physicians, by Dr. J. Hughlings Jackson, who chose for his subject the " Evolution and Dissolution of the Nervous System," and gave what may be regarded as a highly-condensed summary of the results of the work that has occupied him for many years. At frequent intervals Dr. Jackson has published, in somewhat fragmentary form, the results that he has arrived at in localised districts of his field of work ; but these publi- cations have been distributed over so long a period and disseminated in so many journals that they are not readily available for reference. These lectures are therefore welcome as a recapitulation in an accessible form of much that has appeared before ; as giving the latest outcome of Dr. Jack- son's labours ; and as presenting his views in a more unified or, as he might himself term it, integrated form than they have yet assumed. Dr. Jackson regards the central nervous system as a hierarchy ; in which each grade controls the grade below and is controlled by the grade above ; each grade represents over again and co-ordinates in more elaborate combinations the parts represented and co-ordinated by the grade below ; and every part or region or centre of a grade represents a larger share of the organism than any corresponding part of the grade below, a more limited share than any corresponding part of the grade above. Thus each centre in the lowest grade represents but a limited portion of the organism, and each centre in the highest grade represents the whole of the organism, but in no two of these latter centres is the whole organism represented in quite the same way. The whole of the grades are grouped in three main divisions lowest, middle, and highest centres. Of these the lowest are the most completely organised, the highest the least completely organised. When disease attacks the nervous system there are always two sets of manifestations : negative and positive loss of function and excess of function. The func- tions lost are those of the centres diseased. The functions that are excessive are those of healthy centres subordinate to the centres diseased, and per- mitted to act excessively by the removal of the control normally exercised by the centres now diseased. The centre whose function is abolished may belong to the lowest, to the middle, or to the highest division, affording examples of local dissolution. On the other hand there may be a uniform dissolution, the whole of the highest grade of all being first lost, and suc- cessive grades being pared off as it were, as if in layers. Dr. Jackson applies these doctrines, with many subsidiary hypotheses, to every kind of nervous disorder, from atrophy of muscles to insanity, and from giddiness to coma ; and from his vast knowledge of diseases of the nervous system he is able to supply an apparently limitless profusion of instances to every section and subsection of his subject. A more extended account of these important lectures is reserved to a future occasion. [C. M.] At the meeting of the Aristotelian Society on March 17th, the study of Hume's Treatise of Human Nature was continued by a paper on Book i. ?