WHAT WE DO WITH OUR BRAINS 5 



If a million cortical nerve cells were connected 

 one with another in groups of only two neurons each 

 in all possible combinations, the number of different 

 patterns of interneuronic connection thus provided 

 would be expressed by 10^-7^^'°°°. This, of course, is 

 not the actual structure, as we shall see; but the 

 illustration may serve to impress upon us the incon- 

 ceivable complexity of the interconnections of the 

 ninety-two hundred million nerve cells known to 

 exist in the cerebral cortex. 



Every neuron of the cerebral cortex is enmeshed 

 in a tangle of very fine nerve fibers of great complexi- 

 ty, some of which come from very remote parts. It is 

 probably safe to say that the majority of the cortical 

 neurons are directly or indirectly connected with 

 every cortical field. This is the anatomical basis of 

 cortical associational processes. The interconnections 

 of these associational fibers form an anatomical 

 mechanism which permits, during a train of cortical 

 associations, numbers of different functional combi- 

 nations of cortical neurons that far surpass any figures 

 ever suggested by the astronomers in measuring the 

 distances of stars. And in the cortical association 

 centers it is the capacity for making this sort of 

 combination and recombination of the nervous ele- 

 ments that determines the practical value of the 

 sytem. 



In the retina of each eye it has been estimated by 

 Krause that there are about one hundred and thirty- 



