COMPARATIVE LOCOMOTION 



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movement executed may be the same. It is by thus 

 analyzing the types of locomotion proper to a large 

 number of species that the necessary data is forth- 

 coming for determining the association between form 

 and function.* 



In returning to the study of man, the significance 

 of individual peculiarities in the structure of the 

 body will make itself apparent. The variation in 

 length of the bones of the limbs, or in the develop- 

 ment of certain muscles, so noticeable among certain 

 races of men, connects each human type with some 



Fig. 184. — Movements of an elephant's bind leg in executing a step. 



species of animal with similar characteristics. If, for 

 instance, the development of the gastrocnemius muscle, 

 or extensors of the thigh, in a man suggests a resem- 

 blance to a leaping animal, it may be concluded that 

 this man will probably possess special aptitude for 

 jumping, and so on. 



Comparative Locomotion among Birds. — We know 

 that there are two distinct types of wing among 

 birds, each suitable for a different kind of flight, the 

 " sailing " flight and the " rowing " flight. Birds that 

 sail possess narrow wings ; shorter and broader wings 

 are peculiar to those that use them as oars. If the 



* See Marey, Recherches Experiment ales sur la Morphologie des 

 Muscles. C. K. de l'Academie des Sciences, September 12, 1887. 



