General Discussion 51 



lie is eiglity, l)iit you don't find i)ooplo writino a i)lay like Macbeth at 

 eighty. There is a differenee between the kind of aeliievenient thai is 

 possible in later life and really maximal achievement - sueli ;»s Xe\\t<»n 

 writinji: his l^rincipitt before he was fort\-. 



Lanshifi: And I beheve it was nenerall\ aronnd the aj^e of thirty in 

 most instances. 



Lenis: ^W11, it varies for different occupations — chess champions 

 were always under thirty-five. But Lehman gives detailed figures for 

 the different occupations. I think it is one of the dangerous failings of 

 our society, that it tends constantly to elevate the age at which people 

 are given responsibility and opportunity. More and more qualifications 

 and training are required before people can tackle a job instead of letting 

 them try at the age when they will do it best. 



Olhrich: I would like to ask Prof. Lewis if it is possible that cerebral 

 function can be measured in terms of blood supply to the brain? We 

 found by means of a semi-quantitative measurement that with advanc- 

 ing years the cerebral blood flow decreases. We applied the d\'e method, 

 measuring the dye distribution between the two hemispheres. For 

 example, if we give dye into the right carotid artery and compare the 

 dye content of the two internal jugular veins, Ave find that in normal 

 younger persons 80 per cent of the dye is on the same side and 20 per 

 cent on the contrary side. Now, when a focalizing lesion sets in, this 

 difference between the sides decreases. The question is, is it possible to 

 measure the blood flow, the sugar uptake, and uptake in the brain as 

 accurately as possible and correlate these findings with the facts of dye 

 distribution? There are, we found, differences between different classes 

 of workers. The miner shows a different blood flow to the brain from 

 that of the intellectual. It may be of gTcat interest to see how one could 

 correlate these changes in blood flow with such functional measurement 

 as the psychiatrist or psychologist may try to do. 



Lezvis: Prof. Himwich made some observations on this matter — he was 

 concerned with arteriovenous oxygen differences and not blood flow, 

 but I take it that it's cerebral metabolic rate that is important. And 

 Norman Cameron, approaching that in a different way, tried by altering 

 the blood flow through the brain in old people to see whether there was 

 any alteration in the capacity to perform intellectual tasks; he wasn't 

 able to demonstrate it. I think Dr. Freeman knows more about this 

 than I do. 



Freeman: We have done some studies in connection with people 

 getting hormones, but I think I could tell you better about it after 

 Betty Rubin has given you the information she has on that. But 

 certainly over a period of administration of large amounts of hormones 

 there was no particular change in psychological functions. 



Comfort: Prof. Lewis has discussed the way in which deterioration of 

 change in psychological function is related to biological processes. I 

 wonder if he could say something, perhaps, in the other direction, about 

 the way in wliicli the apparent rate of senescence, as judged by general 

 health, can be influenced by psychological factors. I went through the 

 lists of obituary notices of members of a couple of small learned societies 



