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4 66 SCIENCE PROGRESS 



but transformers of energy, and they use up ox}^gen in the 

 vital functions associated with this specific transformation. 

 Moreover, traces of the specific effects are left in the perceptor 

 cortical neurones constituting memory. Now what will be 

 the effect on the growth of the neurones forming the central 

 perceptor for vision, if the child is born blind, and all light 

 stimulus is thereby cut off from the brain ? Experiment has 

 answered this question. A microscopic examination of the 

 visual area of the brain of a puppy whose eyes were removed 

 at birth was compared with a normal puppy, and the accom- 

 panying figures show that the cells of the grey matter of the 

 blind dog were small and shrunken as compared with the cells 

 of the grey matter of the normal dog. Stimulus, therefore, 

 is necessary for development and growth of the neurone. 



Helen Keller and Laura Bridgeman in Relation to the 



Tactile-Motor Sense 



You may ask how it was that Laura Bridgeman and Helen 

 Keller, both blind and deaf in early life, were able to develop 

 such a high degree of intelligence when the two principal 

 avenues of intelligence were cut off in early life. My answer is 

 this : Look at this diagram of the child's brain at three months 

 and you see every part of the grey matter of the cortex is 

 connected by fibres capable of functioning; all the elementary 

 perceptor centres of the special senses are connected by associa- 

 tion fibres with the kinaesthetic sense area and the motor efferent 

 area. The child at three months is no longer capable of an 

 elemental sensation ; the visual and tactile-motor senses have 

 become associated ; the child has learnt to handle things seen 

 and to memorise the meaning of things seen, as regards other 

 qualities than form and colour. Now both Laura Bridgeman 

 and Helen Keller were not affected with blindness and deafness 

 till such a time after birth had elapsed for a very complete 

 development of the association systems. Sensory stimuli had 

 poured in through all the sensory avenues for twenty-six months 

 in the case of Laura Bridgeman and for nineteen months in the 

 case of Helen Keller ; consequently we should not expect those 

 regions of the brain which had served for seeing and hearing 

 — which had been shut off by damage to the transmitter — to 

 undergo atrophy and arrest of development the same, as if no 

 stimulus of light or sound had ever affected them. It may be 



