November 6, 1902] 



NA TURE 



the psychologist may be tempted to content himself with 

 the cursory review that is alone possible in such a work. 

 It should certainly be possible nowadays for the writer 

 on psychology to assume on the part of his readers a 

 competent knowledge of the gross anatomy of the nervous 

 system and of the principles of the conservation of 

 energy. (In the anatomical section occurs an error that 

 is, perhaps, of the nature of a slip. In Fig. 79 and in 

 the accompanying text the uncrossed fibres of the optic 

 nerves are represented as going to the nasal sides of the 

 retinas. Now although v. Kolliker and others still main- 

 tain that the decussation of the optic nerve-fibres in the 

 chiasma is complete, and although there is some ground 

 for believing that there occur considerable individual 

 variations in the proportion of crossed and uncrossed 

 fibres, yet all authorities agree that the uncrossed fibres 

 go to the temporal sides of the retina;.) The propriety 

 of including an account of the general physiology of 

 nerves is less open to question, the less so as Prof. 

 Wundt is here on his own ground and can speak with 

 authority. In this section Wundt makes a timely 

 protest against the uncritical acceptance and wholesale 

 application of Hering's doctrine of assimilation and dis- 

 similation now so common among physiologists, and yet 

 he teaches somewhat dogmatically a view that differs 

 but little from the one he rejects. He too groups 

 together under the term "inhibition" (Hemmung) all 

 phenomena to which it can in any sense be applied, and 

 assumes that one and all are manifestations of constructive 

 metabolic processes, thus affording one more instance of 

 the fact that the study of logic cannot prevent a man 

 forming illogical conclusions. It cannot be too frequently 

 pointed out that we have no evidence of active inhibitory 

 processes within the nervous system and that all the 

 numerous cases of " inhibition " may, and in the present 

 state of knowledge should, be regarded as cases of 

 interference or prevention only. Wundt goes so far as 

 to assume a differentiation of the bodies of nerve-cells 

 into two parts, the anabolic inhibitory and the katabolic 

 augmentor parts, and applies this hypothesis to the 

 explanation of the valve-like nature of the paths of the 

 spinal cord. But although the hypothesis seems to have 

 been devised in order to explain this phenomenon, it is 

 not by any means clear that it can be made to do so. 



The discussions of the functions of the cortex and 

 especially of the " speech-centres " are admirably thorough 

 and suggestive, and here Wundt gives a great develop- 

 ment to the conception of a "brain-centre." It is, 

 perhaps, to be regretted that he retains the term 

 "centre," for it properly expresses a crude conception 

 of which the period of usefulness is now at an end. 



In treating of the fundamental constituents of psychical 

 processes, Wundt distinguishes two fundamental kinds of 

 psychical element, the sensations and the feelings (Emp- 

 findungen und Gefuhle), the former including all those 

 that have an objective reference and that are determined 

 directly or indirectly by stimulation of sensory nerve- 

 endings both within and on the surface of the body, the 

 latter being the purely subjective elements. Com- 

 pounded of sensations is the presentation (Yorstellung) 

 and of feelings the emotion (Gemiithsbewegung). 

 Wundt thus sets aside the old distinction of sensation 

 and idea as that which is excited from without and from 

 NO. 1723, VOL. 67] 



within respectively, asserting that the distinction is 

 purely logical and not at all psychological. Though we 

 may admit that Wundt's use of the terms is a convenient 

 one, yet it is impossible to follow him in denying the 

 psychological character of the distinction usually made 

 by English authors, or to admit his claim that the 

 occurrence of hallucinations, which are purely patho- 

 logical states, necessitates this denial. If the distinction 

 were not psychologically valid, if we did not immediately 

 recognise in the presentation the peculiar quality of 

 reality that distinguishes it from the representation, the 

 term hallucination would have no meaning. 



Perhaps the most interesting part of the volume is the 

 discussion of the " law of specific nervous energies." 

 This principle Wundt would replace by one which he 

 declares to be directly opposed to it, and which he de- 

 scribes as " the principle of the adaptation of the sensory 

 functions to the stimulus and of the sensory apparatus to 

 the functions." This is based upon and assumes the 

 truth of the following principles : that of the original 

 similarity of function of all nerve-elements, which Wundt 

 establishes by tracing in a most interesting manner the 

 differentiation of the various senses from the general sen- 

 sibility of the amceba upwards ; the principle of the 

 adaptation of nerve-elements through use or habituation ; 

 and the possibility, which we seem compelled to assume in 

 some cases, that nerve-elements may come gradually to 

 discharge the functions of others when those others are 

 in any way rendered incapable of functioning. Now, 

 admitting that the "law of specific nervous energies," 

 as set up by Johannes Muller and by Helmholtz, is not in 

 any sense an explanatory principle, but merely a resume 

 of a large group of facts, and admitting that it demands 

 genetic treatment such as Wundt supplies, yet it is not 

 possible to admit that even the most complete account of 

 the evolution of the specific differentiations of sense can 

 abolish the truths of which this "law" is the summary 

 expression ; to account for the origin of a thing or 

 belief is not necessarily to explain it away. The fact 

 remains that any specialised nerve of sense, when 

 subjected to stimuli whether normal or abnormal, leads 

 only to the kind of affection of consciousness peculiar 

 to that sense. Wundt's account of the adaptations of 

 the senses to stimuli is admirable and no doubt true so 

 far as it goes, but it is far from being a complete 

 explanation of the genesis of the specific functions. 



Reducing the problem to its simplest terms, suppose 

 a primitive sense-organ to be affected in the same 

 way by two classes of stimuli, say two rates of vibra- 

 tion of the circumjacent medium — and then suppose 

 that either rate of vibration comes in the course of evo- 

 lution to determine a differentiation of one part of the 

 nerves of the organ, so that one set of nerves comes to 

 respond in one way to the one vibration-rate only and the 

 other set in another way to the other (or that all the 

 nerves come to respond in two distinct ways), and sup- 

 pose the difference of response to consist in a difference 

 in rate of vibration of the substance of the nerves, or in 

 a difference of propagated chemical changes. Up to 

 this point we may accept Wundt's account of the differ- 

 entiation-process as adequate. But when we inquire — 

 How comes it that the soul reacts to these two vibration- 

 rates (or two kinds of chemical change) with two different 



