R. W. GERARD 35 



ability that the engram in neurones, which themselves undergo 'regeneration' by 

 changing their material three times a da\', might also be something at a molecular 

 level. Whatever the mechanism, in either case, a new kind ot template is formed, 

 new molecules are reproduced according to the template, and this is the way 

 fixation ot experience or learning is carried on in the nervous system. 



Thorpe. With regard to this matter ot the planaria there have been a number of 

 examples of what have been called pre-imaginal conditioning in insects where the 

 larva was exposed to an intluence which produced the corresponding modification 

 of behaviour in the adult. This was first done with regard to exposure to chemical 

 substances, but there was also a series of experiments reported by Borell du Vernay 

 (1942) in which the larvae of the beetle Tciiehrio iiwliter were trained to take a 

 certain path in a 'T' maze and the same effect was observed significantly in the adults. 



Gerard. To what extent is the nervous system discontinuous? 



Thorpe: A steady change takes place. Although the locomotory systems of the 

 larva and the adult are very different there would certainly have been organized 

 nervous tissue present throughout. So, though we are not here dealing with a 

 complete replacement of nervous tissue, I think nevertheless that these experiments 

 are interesting to recall in connection with the subject of our present discussion. 



Might I ask you about one other point? A very different one. You referred to 

 this matter of fixation and recall and the distinction between it. I was very puzzled 

 some years ago by some work that Dr McCulloch reported, on the ability of some 

 patients to recall, when under hypnosis, extraordinary details of their own early 

 actions and experiences. One particular case I remember concerned a bricklayer 

 who was able to recall minute details of the bricks he had laid at a certain date of his 

 life. I tried to get the exact particulars ot this trom Dr McCulloch at the time but 

 he was not able to give anytliing like the detail which I hoped would be torth- 

 coming. I mentioned it in the hope that other people here, such as Dr Hebb, 

 might have some fresh data to give us on this particularly important topic. Only 

 last year Wilder Penfield {Pwc. Nat. Acad. Sci., 44) stated his belief, based on 25 

 years experience ot surgical treatment of brains of epileptics, that the temporal 

 lobes possess a permanent record of the stream of consciousness in amazing detail 

 — as if the brain cells behaved like a tape recorder which may be played back by a 

 suitable electrical stimulus. 



Gerard. I have also been intrigued by that report. As I recall, a bricklayer in his 

 sixties or seventies was asked to describe, say, the fifth brick in the seventh tier of a 

 wall that he had laid in his twenties. The bumps on the top and the bottom of the 

 brick he described under hypnosis could be checked and they were there. It is a 

 dramatic statement and I have referred to it in a paper. I do hope McCulloch is 

 correct, for he is also my source. 



Another example, given informallv, at a symposium in Kansas City along with 

 the statement about recall of events under deep surgical hypnosis, frightened me 

 even more, because it makes me think ot Bridie Murphy. An adult was asked to 

 recall some details of a classroom, desks, etc., in which he sat when 6 years old. He 

 was quite unable, even under hypnosis, to recall any of these things until the 

 suggestion had been made: 'You are now 6 years old'. Then he described them. 

 When he was told he was 7 years old, he couldn't do so. I can only say that a 

 thoroughly reputable psychologist told us this with fear and trembling, but he 

 could not find anything wrong with his experiments. 



D 



