HIS PHILOSOPHICAL POSITION 



Notions of extent and of movement are not derived 

 necessarily from visual perceptions, but from the 

 feeling of movement due to muscular contractions, 

 and even to the degree of innervation felt to be 

 necessary for a particular movement. Other im- 

 pressions are added to those of the visual organs ; 

 thus the eyes or head are moved so as to see the object 

 in different positions ; it is touched, etc., and the 

 ensemble of all possible sensations gives rise to the 

 representation of the object to the mind. This is 

 perception, when applied to actual sensations, or it 

 may be a representation due to memory. The 

 psychical act is the association of the signs derived 

 from the organs of sense, or the association of re- 

 presentations. 



In 1866, two elaborate papers appeared on the 

 axioms of geometry ; a synopsis of these was placed 

 before English readers in 1870 ; l there was a popular 

 lecture on the same subject in 1876; in the same 

 year, and in 1877, two papers were published on 

 the origin and meaning of geometrical axioms, 2 

 and in 1894, the year of his death, a last 

 paper on the accurate explanation of sensory im- 

 pressions. 3 



There can be no doubt the researches of Helm- 

 holtz into the phenomena of single vision with two 



1 The Academy ) vol. i., p. 128. 



2 Mind, vol. i., p. 301 ; also vol. iii., p. 212. 



3 Zeitsch.fur PsycAologie und Physiologic der Sinnesorgane, Bd. 7, s. 18. 



2 59 



