46 STELLA BURNHAM VINCENT 



Other conditions. The strictly land forms were inactive and 

 evidently more dependent upon vision for locomotion.-" 



Thus Mr. Mills observations were confirmed. This sense of 

 support in the land animals is a strong fundamental sense from 

 whose control, under the necessities of self preservation, vision 

 has, in a way, partly freed it by associating with it perception 

 of space which renders inoperative within certain limits the 

 inhibitory influence. 



These are not the only observations on the subject. Small^' 

 found the same hesitancy in young white rats, Miss Allen" none 

 in the guinea pig, while Thorndike's chicks,-^ four days old, 

 jumped at ten inches, hesitated at twenty-two and did not 

 attempt thirty-nine. 



We are very apt to think of sensory endings as organs for 

 knowledge, for reflecting the exterior environment and to forget 

 that a large part of our sensory experience arises within the 

 body itself and is concerned immediately with the primal needs 

 of the organism. 



A water animal supported by the fluid in which it lives does 

 not have the double problem in locomotion which a land animal 

 has. The escape from the water and the acquirement of swift 

 locomotion has been the slow process of ages. An immense 

 increase in muscular power was made necessary by this change. 

 To the sensory control in this task all of the existing sense 

 organs contributed but they were modified by the need of definite 

 orientation, and of swift locomotion for the preservation of the 

 race and the species under new and difficult conditions. The 

 modification of the ear has already been spoken of, the eye 

 changed from monocular to binocular, from peripheral to foveal 

 vision, ^"^ and in muscles and joints, in sinews and extremities 

 sensory nerves multiplied to furnish control for the difficult 

 equilibration necessary in locomotion. 



Not only in phylogeny but in ontogeny as well is locomotion 

 a difficulty to be conquered, a difficulty requiring the aid of 



2" Yerkes, R. M.: Study of Space Perception, Jour. Comp. Neur. & Psychol., 

 1904, vol. 14, p. 17. 



"Small, W. S.: op cit., p. 305. 



22 Allen, Jessie: Association in the Guinea Pig, Jour. Comp. Neur. <& Psychol., 

 1904, vol. 14. 



23 Thorndike, E. L.: Animal Intelligence, p. 159. 



2^ Note: — It is not to be understood that this development has no other func- 

 tional correlates. 



