584 CRITICAL NOTICES I

nexion with consciousness ; but no mention is made of sensations of equilibrium, motion and dizziness with which they are supposed to be concerned. Prof. Ladd is known to us as the translator of Lotze's Dictate, and Lotze was one of the first, in Wagner's Handworterbuch der Physiologie, 1843, to take a stand against the then prevalent vitalism and attempt to subject living tissues to the laws of matter in motion. This mechanical theory of life is now generally accepted, and it is no wonder that Prof. Ladd emphasises it both in the name of the section, " The Nervous Mechanism," and in his treatment of the subject. Thus he says (p. 216) : " The aim of physical research with regard to any given system of this kind is, therefore, not accomplished until all the movements of its different parts are explained in the light of a consistent mechanical theory. This general principle of all physical science neither needs nor permits a special exception in the case of the human nerves, organs of sense and brain." Therefore we cannot be other than surprised when Prof. Ladd afterwards advocates a theory of interaction and causal relations between mind and body in sheer contradiction to a mechanical theory of living tissues, even saying (p. 665) : " For aught we know, it is of the nature of atoms, when they are brought into relations so extraordinary as those which prevail in the nervous system, to behave with reference to each other in a way that is wholly irre- ducible to any simple formula like that of the conservation and correlation of energy ". Prof. Ladd's account of the nervous system, taken as a separate treatise, is clear and accurate, perhaps the best in our language. It is, however, possible that the 219 pages and 82 illustrations would have been of more service if they had been given to the real subject of the work. This subject, physiological psychology or psychophysics, is treated in the second part, taking up slightly less than half the book. The first two chapters are on " The Localisation of Cere- bral Function," and deal with matters at present in sad confusion. Prof. Ladd's review seems to be on the whole careful and judi- cious. He perhaps lays too much stress on the results of Prof. Exner, whose manner of illustration, beautiful as it is, is somewhat misleading : the surface of the brain is divided into little areas, which are printed darker as the percentage of cases increases in which the area was diseased in connexion with a particular motor or sensory disturbance; thus, if there were only one case the area would, possibly by mere chance, be quite white or quite black, and seem more positive than the grey obtained from a large number of cases. Prof. Horsley's interesting surgical operations at the Queen's Square Hospital are, perhaps, too recent for mention. Aphasia is treated somewhat briefly con- sidering its importance and the valuable monographs we have on the subject by Kussmaul and others. Prof. Ladd does not seem justified in stating, and in italics (p. 284) :