July 28, 1887] 



NATURE 



291 



test against a merely materialistic interpretation of the 

 phenomena. Such a protest,, coming from one who is 

 well abreast of modern physiology, is likely to carry 

 weight which could not but be lacking to the opposition 

 of a thorough-going disciple of the "old psychology" 

 school. No one can say that Mr. Ladd's conclusions are 

 reached in and through his ignorance of the real nature 

 and value of the facts on which materialists base their 

 arguments. 



The work consists of a short introduction and three 

 parts, of which the first deals with " The Nervous 

 Mechanism," the second with " The Correlations of the 

 N'ervous Mechanism and the Mind," and the third with 

 ' The Nature of the Mind." 



The first part opens with a chapter on the elements 

 of the nervous system, and then proceeds to show how 

 these elements are combined into a systematic whole. 

 The morphology of the nervous mechanism havingthus 

 been described, its general physiology is dealt with in the 

 next two chapters, and the automatic and reflex-motor 

 functions of the central mechanism are successively 

 brought under review until, in ascending order, we reach 

 the cerebral hemispheres, the special functions of which 

 are reserved for the second part. The reasons the author 

 gives for adopting this plan are: (i) that nothing is 

 known as to the molecular structure of these hemispheres, 

 or as to tlieir automatic and reflex-motor centres and 

 activities which adds anything of importance to the 

 description of the nervous system as a mechanism 

 or to the mechanical theory of its action ; and (2) 

 that the correlations which exist between the struc- 

 tural condition or physiological function of the nervous 

 system and the phenomena of mind are chiefly (if 

 not wholly) capable of study as illustrated in the 

 cerebral hemispheres. An important chapter on the 

 end-organs of the nervous system then follows, and is 

 succeeded by one on development. A concluding chapter 

 in this part is devoted to the mechanical theory of the 

 nervous system, in which, while the author admits that 

 the changes which take place in the brain are essentially 

 the same as those with which the science of molecular 

 physics has elsewhere to deal, he reaches the conclusion 

 that " it cannot be pretended that even a beginning has 

 been made toward a satisfactory theory of the functional 

 activity of the central organs considered as a special case 

 in molecular physics." 



In this part, together with much that is familiar, there 

 is not a little that has hitherto seen the light only in 



altered publications. 



The second part opens with two long chapters on the 



calization of cerebral functions. The experiments and 



nclusions of Fritsch and Hitzig, Exner, Ferrier, Munk, 



oltz, and others are carefully described and considered. 



he conclusions to which the author is led by his review 



f these labours are as follow : — 



" Three principles may be laid down as summing up 

 the results reached by inference upon the basis of experi- 

 ment with respect to the localization of function in the 

 cerebral cortex. The first principle is to be accepted in 

 the form of a general postulate derived from a study of 

 the other parts of the nervous system, and confirmed on 

 attempting to apply it to the cerebral hemispheres. It 

 maybe stated as follows : the different elementary parts 

 of the nervous system are all capable of performing its 



different specific functions when, and only when, they 

 have been brought into the proper connexions and have 

 been exercised in the performance of those functions. 

 This principle includes two important laws which, we 

 know, hold good throughout the nervous mechanism, and 

 which lie at the physical basis of important psychical 

 facts and laws ; they are the lau of Specific Energy and 

 the laij of Habit. The remaining two of the three 

 principles alluded to above may be said to follow from 

 the first : thty are the principle oi localized function and 

 the principle of substitutio7t. The former asserts that, 

 in the normal condition of the nervous system, all parts 

 have not the same definite functions. Everything in 

 both its anatomy and physiology indicates that the 

 principle of localized function does apply, in some 

 sort, to the cerebral hemispheres. .So-called 'centres,' 

 however, arc in no case to be regarded as portions 

 of the nervous substance that can be marked off 

 by fixed lines for the confinement of definite functions 

 within rigid limits. These areas are somewhat different 

 for different brains of the same species ; they widen when 

 a heightened energy is demanded of them ; their centres 

 are neither mathematical points nor very minute collec- 

 tions of cells. Nor are these areas perfectly isolated 

 localities ; on the contrary, they obviously overlap each 

 other in certain cases. Furthermore, the functions of 

 the cerebrum are not absolutely confined to those centres 

 with which, under ordinary circumstances, they are 

 chiefly or wholly connected ; in which, that is to say, 

 they are localized. If such centres, for any reason, 

 become incapacitated or relatively unfitted to perform 

 their normal functions, the same functions may be per- 

 formed by other areas of the cerebral cortex, provided 

 these areas also stand in the proper connexion. This is 

 the principle of substitution." 



In the remaining chapters of the second part we are 

 led to consider sensations in their qualitative and quan- 

 titative relations, the nature of " things," or the present- 

 ations of sense (which introduces us to " space- form "), and 

 the time-relations of mental phenomena (which intro- 

 duces us to " time-form "). Then we are conducted, 

 through feeling, to the higher faculties — memory, will, 

 conception — the physiological basis of which is sought in 

 vain. The concluding chapter of this part gives a sum- 

 mary of the general correlations of body and mind. The 

 author seems to intend that two points shall standout pro- 

 minently : first, the essentially synthetic activity of the 

 mind in constructing those presentations of sense which 

 we call things or objects ; and secondly, notwithstanding a 

 vague correlation, the inconceivability of any physiologi- 

 cal basis thereof. " For that spiritual activity which 

 actually puts together in consciousness the sensations, 

 psycho-physics cannot even suggest the beginning of a 

 physical explanation." And again : " When we speak of 

 a physical basis of memory, recognition must be made of 

 the complete inability of science to suggest any physical 

 process which can be conceived of as correlated with that 

 peculiar and mysterious actus of the mind, connecting its 

 present and its past, which constitutes the essence of 

 memory." 



In the third part the conclusion to which especial pro- 

 minence is given is this : that the subject of all the states 

 of consciousness is a real unit-being, called mind ; which, 

 is of non-material nature, and acts and develops accord- 

 ing to laws of its own, but is specially correlated with 

 certain molecules and masses forming the substance of 

 the brain. The nature of this correlation is considered 

 at length. To speak of mental states and processes as 



