NA TURE 



THURSDAY, MAY 19, 1910. 



THE COMPARATIVE PHYSIOLOGY OF 

 RESPOySE IN ANIMALS, 



Imwelt und Intieniuelt der Tiere. By Dr. J. von 

 Uexkiill. Pp. 259. (Berlin : J. Springer, 1909.) 

 Price 7 marks. 



THIS is one of the most interesting summaries of 

 biological work that has appeared recently. 

 W ritten by one who has had a large share in physio- 

 logical research, it deals in an intimate manner with 

 the comparative physiology of reflexes among the 

 lower animals and with the adaptation of structure 

 and function to varying habits in the case of allied 

 genera. The inflMJ|ilfiof Sherrington's work is very 

 "bvious, and is suitably acknowledged, but whereas 

 the integrative action of the ner\ous system " is a 

 profound studv of the higher animals, the present work 

 attempts the same analysis of action in various lower 

 types, and then synthesises conduct in the light of 

 the reactions so displayed. The anatomical know- 

 ledge required for this purpose is not great, and the 

 technical physiological difficulties of terminology, 

 though more fcwmidable, are not insuperable, ^^'hen 

 these are acquired, the analytic skill of the writer in 

 delineating the inwardness of animal movement be- 

 comes a source of real pleasure. 



The main theme of the book is to discriminate (i) 

 the effective external stimuli that constitute the 

 " Umwelt " of each selected group cr typical example ; 

 (2) the ner\-ous stimuli set up within these creatures 

 and forming the " Innenwelt," and (3) the sense of 

 perception or "Gegenwelt" that arises in the 

 " brain " of the higher groups. What part of its 

 environment really aff^ects an amoeba, a sea-anemone, 

 or a jelly-fish can only be determined by a study of its 

 reactions, by an analysis of its neuro-muscular 

 activities. Hence the need for a renewed analysis of 

 muscular action and of nervous control. Accordinglv, 

 in each chapter the author, with a few vigorous sen- 

 tences, sketches out the habits and movements of the 

 type selected, and the dominant features of its mus- 

 cular and nervous topography. A more detailed 

 account of its reactions in relation to its mode of life 

 is then given. Finally, the muscular action in re- 

 lation to nerv'ous stimulation is dealt with in detail, 

 and the effective outer and inner world of the creature 

 is summed up in a few lines. 



The nature of protoplasm and the origin of struc- 

 tural organisation form the problems of the first 

 chapter. " Does protoplasm possess a structure or is it 

 a fluid ? " is a question that has been varyingly 

 answered for the last eighty years. Even if we agree 

 with BiJtschli and Rhumbler in assuming a certain 

 structure in fluid protoplasm when at rest, the be- 

 haviour of " streaming " protoplasm (as in Amoeba 

 and cyclosis) forbids the assumption that any struc- 

 ture persists when the mass flows and points to its 

 essentially fluid unorganised nature. Thus the first 

 paradoxical property of this living substance becomes 

 NO. 2 1 16, VOL. 83] 



apparent, namely, its power of converting a fluid into 

 an organ, into a series of organs, and then of with- 

 drawing these and resuming its structureless con- 

 dition. The Amoeba or the digestive cell of a lowly 

 worm " puts out *' a highly organised process made 

 from fluid unorganised protoplasm, and, having there- 

 with enclosed some food, withdraws this appendage. 

 The undifferentiated egg of animal or plant becomes 

 organised, and the organisation may become resolved 

 under adverse conditions into a structureless mass 

 (as in the " brown-bodies " of Polyzoa), which is re- 

 organised as more favourable conditicwis recur. This 

 property of morphogenesis and regeneration separates 

 living things from all machines, and when taken to- 

 gether with the phenomena of " regulation " 

 (physiological changes in organisms consequent on 

 stimulation), it shows, in the author's words, the 

 supra-mechanical nature of the origin of structure, 

 however mechanical the functions of organisation may 

 be 



The physical basis of life is indeed a paradox. Its 

 organisation hinders rather than helps additicmal 

 complexity, for that which is to constitute the addi- 

 tion has to be made, not out of what is already 

 organised, but out of what has been left over of the 

 uncM-ganised protoplasm, and in this process not a 

 present, but a future, mechanism determines the pro- 

 cess. We think of action as the relation of precedent 

 to consequent, but in protoplasmic action, what is 

 consequent determines the initial stages of change. 

 Animals and plants arise like a musical composition 

 in which the later parts condition the earlier ones, 

 even though they are only reached through the open- 

 ing bars or movements. They are not like machines, 

 unities in space only. They are also unities in time. 

 In this sense von Baer's metaphor is magnificently 

 expressive. Organisms arise, he says, like a kind of 

 melody. 



From this preface the author passes to a systematic 

 treatment of invertebrates. On the basis of Jenning's 

 researches, he concludes that Amoeba (or at least 

 Atnoeba terricola) responds only to three kinds of 

 stimuli — mechanical, chemical, and luminous. Para- 

 mecium, by a series of delicately poised adjustments, 

 "rests more safely in its environment than a child in 

 its cradle." It is so adjusted that all happenings 

 bring it luck except the arrival of a carnivore of its 

 own kind (Didimium). Far lower than these Pro- 

 tozoa in poverty of response is the ascidian Ciona. 

 The effective environment of this creature during its 

 active larval stage has not been analysed, but the 

 adult sea-squirt is apparently dead to every impulse 

 save one. Only mechanical shocks are recognised, 

 and these in successional order. An interesting study 

 of sea-anemones brings the writer to reflex-actions, of 

 which these animals exhibit three — contraction of the 

 circular muscles, secretion of slime, and contraction 

 of the longitudinal muscles. The influence of tides 

 and of light are certainly felt in littoral species, though 

 in the case of the Mediterranean forms studied by the 

 author their effect is apparently extremely slight. 

 We feel, however, that the light-reactions will prove 

 vastly more important than is here assumed, for the 



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