J. C. ECCLES 351 



trainino;, or massage or mechanical and electrical stimulation, etc., this results in a 

 good trophic state of the limbs and a very rich and lively reflex activity of the 

 caudal part of the transected spinal cord. The precise data obtained by Dr Eccles 

 has importance, not only in general neurophysiology, or in the problem of 

 recovery of functions in injured organisms, but also in the problem of learning. It 

 seems to me that although morphological and functional changes of synaptic 

 apparatus as a result of their excessive use is a common property ot all the nervous 

 structures, nevertheless, these changes lead to an elaboration ot conditioned reHex 

 only in the neural structures ot the higher parts of the nervous system, at least, m 

 high developed organisms. I cannot agree with Shurrager and other authors that 

 the spinal cord is also able to elaborate conditioned reflexes. In any case, Dr Eccles's 

 data shows that achievements in general neurology are and will ever remain a 

 source of investigations of brain processes and especially conditioned reflex 

 research. 



Eccles. Thank you Dr Asratyan. We have very similar experiments going on 

 in Canberra. Dr Kozak from Dr Konorski's laboratory is investigating the changed 

 reflex pattern that occurs in spinalized kittens. There is here evidence that you have 

 new patterns developing in the C.N.S. under changed conditions. 



Fessard. Wotild you consider that an inhibition at the synapse would produce 

 the same effect as a long disuse ? 



Eccles. If the cell does not fire impulses, the synapses that it makes with other 

 cells would be disused. 



Fessard. Disuse obtained by inhibition would be produced in a more natural 

 way than by section of the nerve. Would it be possible technically to make such an 

 experiment? 



Eccles. I have thought about such a possibility but I do not know how to do it 

 experimentally. 



Segundo. Dr Eccles, when vou compared the 'used' side with the "non-used' 

 side, tetanic potentiation was greater in the latter (as measured in reterence to a 

 100 per cent value of the initial monosynaptic response amplitude). How did you 

 select stimulus intensity in order to make effects on both sides comparable 



Eccles. With all experiments there was maximum stimulation of group I fibres 

 and in addition the series were repeated in alternate sequences many times. 



Hebb. I would like to make a comment on a different track. There is some 

 evidence which needs to be considered when you discuss learning over a long- 

 range period. Chimpanzees put into darkness after being raised in light to the age 

 of 6 months suffer complete forgetting of visual responses when brought out 

 again. The clinical ophthalmologist tells us that if a child becomes blind before the 

 age of 2 years he will be indistinguishable from the congenitally blind at maturity. 

 If he becomes blind at the age of 4 years he will never be like the congenitally 

 blind, he is like the person who has had vision until maturit)'. In other words there 

 can be well established visual learning but it will not last if it is not maintained for 

 4 or 5 years. Once thoroughly established, it will last for good. 



Anokhin. In our laboratory we are now doing experiments which have a direct 

 correlation with yours. We have changed muscles from extensor or flexor position. 

 For 3 or 5 weeks these cats presented abnormal movements — but after i 

 year they moved in the normal fashion. The electromyographical analysis shows 

 that the muscles performed their new function. But after spinahzation these muscles 



