Health and Disease 
like mice, much longer in man and larger mammals. If birds 
and mice of comparable size were treated with carcinogens 
would one find that the delay was correlated with the lifespan 
or with the rate of development to maturity? 
There are some remarkable examples of purely genetic 
cancer caused by genetic imbalance, in fish like Platypoecilus, 
and plants like Nicotiana. In Nicotiana a number of species- 
crosses result in cancerous growths, which seem to be quite 
comparable to the cancerous growths in animals. One species, 
and certain individual chromosomes of the species, is especially 
effective in producing cancerous growths. There is a big oppor- 
tunity for research here, since large quantities of plant can- 
cerous tissue can be cultivated in organ-culture. 
As Szent-Gyérgyi suggested, in studying any biological 
process one has to combine reductionist analysis with what I 
call eduction. This means first looking at the end-result of the 
process and its function, or its biological value. Then one can 
try to analyse it into its elementary components and origins, 
and finally see how the process works as a process—how it can 
be upset, how it can be improved. 
There are some interesting sidelights on these problems. When 
I was at the Zoo, I got Dr. Honigmann to do some work on 
digestion in sloths and he found that this was almost as slow as 
their movements. What other basic phenomena of their life 
may be slowed down, I do not know. I don’t even know if their 
expectation of life is very long. 
I was once passing the enclosure of the giant Galapagos 
tortoises and I heard a very curious grunting noise, repeated 
regularly at considerable intervals. I eventually found it was 
made by the giant tortoises while they were copulating. If it 
had been speeded up ten times or so it would have sounded just 
like you or me! 
Pirie: John Hunter, who is so thoroughly enshrined here at 
the Ciba Foundation*, also observed and measured the extreme 
slowness of digestion in the hibernating hedgehog. 
* [The Ciba Foundation houses a small private museum of Hunteriana belonging 
to the Hunterian Society.] 
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