818 EVENING DISCOURSES. 



EVENING DISCOURSES. 



F BID AY, SEPTEMBER 2. 



Types of Animal Movement. 

 By Professor William Stirling, M.D., D.Sc, LL.D. 



The discoveries of great men nvr leav us — thy are immortal, they contain 

 those immutable truths which survive the shock of empires, outlive the struggles 

 of rival creeds, and witness the decay of successive religions.' These are the 

 words of the historian of civilisation, and to them may be added those of Mr. 

 Roosevelt in his Romanes Lecture at Oxford : ' In the world of intellect, doubtless 

 the most marked features in the history of the past century have been the extra- 

 ordinary advances in scientific knowledge and investigation.' We must all admit 

 that modern progress in certain directions is largely due to inventions and dis- 

 coveries the ' offspring of the scientific mind.' 



It seems all the more remarkable, therefore, when we find Von Uexkull in his 

 wonderfully suggestive book, ' Umwelt und Innenwelt der Thiere,' asking the 

 question, 'What is a scientific truth?' He himself gives his reply, 'An error of 

 to-day.' This reply reminds one of other questioners after truth, and also of the 

 remark of Napoleon. ' What is history,' said he, ' but a fable agreed upon ? ' 

 There is food for reflection in these replies, both for the man of science and the 

 historian. I shall try to show you what science has achieved in the investigation 

 of animal movements, and in doing so I must refer briefly to the historical aspect 

 of the question, for it is just two years more than three centuries since the founder 

 of th© study of animal movements was bcrn in the. fortress of Castel Nuovo at 

 Naples. 



Linnaeus, in his oft- quoted maxim, ' Stones grow,' ' plants grow and live,' 

 ' animals grow, live, and feel,' seems to have omitted the most characteristic 

 feature of living animals, for undoubtedly amongst all manifestations of life the 

 features which are most striking, most characteristic, most interesting, and to us 

 most intelligible are of a mechanical order, as represented by movements of various 

 kinds, whether movements of one organ on another or movements of the animals 

 themselves — on land, in water, or through air — the three great Highways of 

 Nature. 



Movement, though not a characteristic of animals alone, is in them so marked 

 as practically to become a distinctive feature. Their immense power of generating 

 mechanical motion enables them to perform those actions which constitute their 

 visible lives. The subject presents an endless field of inquiry to the anatomist, 

 to the physiologist, to the artist, and not least to the pathologist. 



Nothing is more remarkable in Nature than the variety and, on occasion, the 

 apparent simplicity of the mechanisms for the production of movements both in 

 animals and plants. ' Every chemical substance, every plant, every animal in its 

 growth teaches us the unit of cause, the variety of appearance.' As Emerson 

 expresses it, ' Nature is an endless combination and repetition of a very few laws. 

 She hums the old well-known air with innumerable variations.' Perhaps nowhere 

 is this more evident than in the sphere of movement. 



The motor organs themselves have been far more carefully studied than the 

 movements they produce, but there are not wanting signs that the impulse given 

 to morphological studies by the doctrine of adaptation under natural selection has 

 begun to affect the study of purely physiological problems, in proportion as it 

 becomes daily more evident how infinitely fertile are the movements of organisms 

 as a field for the study of adapted reactions. 



