1 62 Instinct and Intelligence 



tration of our eyes on printed words passes to 

 our visual and auditory word centres; a part 

 of their mnemic energy is thus released and 

 excites neighbouring association nervous ele- 

 ments, followed by the discharge of nerve force 

 which by practice travels along association 

 fibres offering the least resistance to psycho- 

 motor centres, and leads to the utterance of 

 word sounds corresponding to those from which 

 the original visual impression was derived. 1 

 The efficient working of a system of this kind 

 is gained by its exercise; any fault in the 

 sensory organs or in the nervous apparatus 

 hinders its perfection, but under favourable 

 conditions the more regular the exercise of the 

 materials involved the more readily do they 

 respond to the energy acting on them ; physio- 

 logical and pathological science corroborates 

 this statement. It has been proved that after 

 the excision of the association nervous sub- 

 stance surrounding a dog's visual centres, or 

 the destruction of the corresponding part of 

 the cortex by disease in human beings, the dog 



1 Halliburton 's Handbook of Physiology (eleventh edition), p. 

 741 ; also A Text-book of Physiology, by Landois and Stirling, 

 Vol. II., pp. 962, 988, 996. 



