486 



SCIENCE. 



ception of an object not actually present, involving 

 the recognition of its absence, an illusion is the sub- 

 jective perception of an object actually present, but 

 in characters which the object does not really possess. 

 With appropriate alterations these definitions will 

 cover the abstract hallucination and phantastic illu- 

 sion of Wundt as well. 



In his second chapter, the author ably, but we be- 

 lieve unsuccessfully, endeavors to defend his refusal to 

 recognize the distinction between illusion and halluc- 

 ination as the leading principle of classification, 

 though he admits the necessity of making this dis- 

 tinction in accordance with the leading alienists. 

 Wundt, an authority whose teachings in psychological 

 physiology the author of the present volume has most 

 successfully assimilated, has drawn attention to the 

 numerous connecting links existing between illusions 

 and hallucinations, and yet strongly insists on utilizing 

 their general differences as a basis of classification. 

 We find the chief drawback to the otherwise great 

 value of the work, in its failure to give adequate space to 

 the anatomical mechanism concerned in false registra- 

 tions of the perceptional and conceptional sphere. If it 

 be borne in mind that while even hallucinations may be 

 based on actual impressions, the latter are not the de- 

 termining factor of the hallucination, the difficulty 

 in discriminating between these perversions is over- 

 come; this is illustrated by the occasional per- 

 sistence of dream-images in the waking state, and 

 the moving of certain hallucinated images conson- 

 ant with the movements of the eye-ball. If an 

 actual or subjective impression, say in the shape 

 of chromatopsia and tinnitus, be granted to exist in a 

 subject hallucinating the vision and voice of the 

 Virgin Mary, it will be instantly recognized by every 

 observant alienist, that the real determining factor is 

 here centrifugal, while in the illusion, which constructs, 

 out of a ball rolling in an ill-lighted apartment, a 

 mouse, the determining factor takes a centripetal 

 course. In the former instance, the misinterpretation 

 lies ready made in the Cortex, and seizes on the slight 

 external pretext, whose existence we only admit for 

 the sake of the argument, to incorporate it, in its sub- 

 stance ; in the latter, it is based upon an imperfect reg- 

 istration and a gradual constructive interpreting pro- 

 cess. Nothing could more forcibly illustrate the cor- 

 rectness of these propositions than the very case cited 

 from Wundt by Mr. Sully of a forester who saw the 

 real objects of the outer world, (furniture and tapes- 

 try, for example,) through the wood piles which formed 

 the subjects of his hallucinations. 



With these remarks on the propositions of the open- 

 ing chapters, our criticism ceases to be adverse. In 

 the last twelve chapters of the book, the author gives 



a concise review of the chief theories held by alienists 

 and metaphysicians on the perceptional illusion, the 

 introspective illusion, dreams illusions of memory, and 

 those of belief. We refrain from again pointing out 

 places where the author encroaches on the fields of 

 delusion and hallucination, as he has given a wider 

 scope to his definition of the illusion, than we are in- 

 clined to consider proper. It is but just to say that 

 he gives a just interpretation to the views of alienists, 

 an interpretation which only occasionally manifests 

 that tincture of uncertainty which is unavoidable on 

 the part of one devoid of a practical knowledge of 

 the insane. 



The perusal of this work cannot fail to be profitable 

 to the student of mental pathology as*well as of met- 

 aphysics. More reliable in the latter field, than in 

 the former, it is yet a successful attempt to present the 

 modern German ideas on the subject, and to combine 

 the teachings of the practical and the abstract psychol- 

 ogists. To the general reader we can only repeat, 

 what we said at the outset, it is the clearest rendition 

 of a difficult yet fascinating theme, to be found in our 

 language. E. C. Spitzka, M. D. 



ON THE DISCOVERIES OF THE PAST HALF- 

 CENTURY RELATING TO ANIMAL MOTION. 

 By J. Burdon-Sanderson, M.D., LL.D., F.R.S. 



The two great branches of Biology with which we 

 concern ourselves in this section, Animal Morphology 

 and Physiology, are most intimately related to each 

 other. This arises from their having one subject of 

 study — the living animal organism. The difference be- 

 tween them lies in this, that whereas the studies of the 

 anatomist lead him to fix his attention on the organism 

 itself, to us physiologists it, and the organs of which it is 

 made up, serve only as vestigia, by means of which we 

 investigate the vital processes of which they are alike the 

 causes and consequences. 



To illustrate this I will first ask you to imagine for a 

 moment that you have before you one of those melan- 

 choly remainders of what was once an animal — to wit, 

 a rabbit — which one sees exposed in the shop of poulterers. 

 We have no hesitation in recognising that remainder as 

 being in a certain sense a rabbit ; but it is a very miser- 

 able vestige of what was a few days ago enjoying life in 

 some wood or warren, or more likely on the sand-hills' 

 near Ostend. We may call it a rabbit if we like, but it 

 is only a remainder — not the thing itself. 



The anatomical preparation which I have in imagina- 

 tion placed before you, although it has lost its inside and 

 its outside, its integument and its viscera, still retains the 

 parts for which the rest existed The final cause of an 

 animal, whether human or other, is muscular action, be- 

 cause it is by means of its muscles that it maintains its 

 external relations. It is by our muscles exclusively that 

 we act on each other. The articulate sounds by which 

 I I am addressing you are but the results of complicated 

 combinaticns of muscular contractions— and so are the 

 scarcely appreciable changes in your countenances by 

 which I am able to judge how much, or how little, what 

 I am saying interests you. 



Consequently the main problems of physiology relate 

 to muscular action, or as I have called it, animal motion. 

 I They may be divided into two — namely (i) in what does 

 i muscular action consist — that is, what is the process of 



