810 PROGRESS OF SCIENCE IN THE CENTURY. 



form and function, but it remains an nncontroyerted 

 fact,"* 



Tens of thousands of neurons go to form the brain 

 and spinal cord of higher animals, and it is certain 

 that they are not homogeneous in structure or uni- 

 form in function throughout. To some degree, at 

 least, there is a localisation of psychical functions. 



" The foundation of a scientific basis for localisa- 

 tion dates from 1870, when Fritsch and Hitzig an- 

 nounced that definite movements followed the appli- 

 cation of electrical stimulation to definite areas of 

 the cortex in dogs. The indication thus given was 

 at once seized upon by David Ferrier, who explored 

 not only the hemispheres of dogs, but those of 

 monkeys and other vertebrates." f Motor and sen- 

 sory areas were distinguished, and the researches of 

 Munk, Beevor, Horsley, Goltz, Schafer, Flechsig, 

 and many others have contributed to the preliminary 

 mapping out of the brain. 



Apart from centres of special sense and motor 

 centres, Prof. Flechsig has distinguished (1806) 

 " association-centres," which he speculatively regards 

 as engaged in the higher intellectual operations. 

 While this interpretation remains quite uncertain, 

 we owe much to the observations by which Flechsig 

 has shown that different centres in the human brain 

 attain their perfect structural development at dif- 

 ferent periods. " When a child is born, very few of 

 the fibres of the cerebrum are myelinnted (let us say, 

 structurally completed), and we have thus an anatom- 

 ical explanation of the reason why nn infant hnl 

 so inactive a brain and is so helpless a creature. It 



* Frefllv trnnslntd from Vorworn, on. cit. 

 t Sir William Tumor, Address Section II, Rep. Brit. At*., 

 1807, p. 785. 



