232 THE PROBLEM OF BODY AND MIND 



Our theory of the relation of mind and body (if it be a 

 relation) must be consistent with what we know of individ- 

 ual development. The intelligent mammal begins its in- 

 dividual life as a pinhead-like cell, and for a long time it 

 must be admitted that psychological methods or formulae 

 are quite inapplicable. The developing ovum of a rabbit 

 (fide Brachet) can go on developing for some time outside of 

 the maternal body, it is a self-contained implicit organism. 

 We do not understand how it is managed, but it has born 

 with it the potentiality of the big brain and the intricate 

 behaviour. There is a gradual emergence of reflexes, of 

 tropisms, of spontaneous exertions, of experiments, of learn- 

 ing, of putting two and two together, of clever behaviour 

 and, in man, of occasional wisdom. In our own case we are 

 sure that as the minute structure of the cerebral cortex in- 

 creases in complexity, the child becomes more intelligent ; 

 as the child becomes more intelligent, the cerebral cortex 

 increases in complexity. Not a single nerve-cell is added 

 after birth, but the inter-relations between the cells increase 

 in number, and the brain becomes' a labyrinth. There are 

 no new nerve-cells, but there is normally no lack of new ideas 

 in the growing boy. 



(b) Our answer to the body and mind problem must be 

 consistent with what we know of the historical facts. In 

 the course of evolution the nervous system has become grad- 

 ually more complex and behaviour gradually more masterly, 

 wider in range, more fertile in resource. We do not wish to 

 make too much of the nervous system, for the method of 

 trial and error, for instance, is practised by animals with 

 no nervous system at all, and a very definite capacity for 

 learning may be exhibited by an animal, like a starfish, 

 without a single ganglion in its body. But when we have 



