546 PHYSIOLOGY CHAP. 



lie perhaps in the numerous commissures, which, since they unite 

 all the convolutions of a hemisphere in the most perfect manner, 

 determine the fundamental unity of the hrain. Is the intellect 

 seated simultaneously in the centrum ovale and the layers of the 

 cortex, or is it seated in the latter exclusively ? I doubt whether 

 in the physiology of the intellect it is possible to neglect the 

 centrum ovale with safety. Admitting, however, that the intellect 

 has the whole brain for its organ, it is not activated at all points 

 of the brain in the same way." 



This statement of Gratiolet, as was opportunely pointed out by 

 Soury, contains almost the whole general modern theory of the 

 localisation of cerebral functions, which has developed in quite a 

 different direction from that of the older phrenology. The latter 

 pictured the brain as divided into so many independent organs, 

 intended for very complex functions. The new theory, on the 

 contrary, endeavours to determine the varying importance of the 

 different parts of the 'brain in so far as they receive centripetal 

 projection paths coming from the different sense-organs, centrifugal 

 projection paths along which the different voluntary impulses are 

 transmitted to the muscles, and commissural and association paths 

 which bring the separate fields of action into close connection. 

 The highest and most complex psychical functions are not localised 

 in these cortical fields, but are conditioned by the associative 

 elements, in so far as these co-operate in making the brain into a 

 \ single organ. The individual acts of the mind result from the 

 different combinations of the intellectual functions of the separate 

 cortical areas. 



IV. From these introductory remarks, though brief and 

 incomplete, it will be readily seen that the theory of sensory 

 and motor cerebral localisation was already formulated in the 

 abstract, and only called for experimental evidence and better 

 definition, when Hitzig aud Fritsch (1870) published their first 

 memoir, " On the electrical excitability of the brain," which formed 

 the brilliant opening of a new chapter in cerebral physiology. 



All the most experienced experimenters Magendie, Longet, 

 Matteucci, Van Deen, Budge, Schiff believed that the nerve- 

 centres of the cerebrospinal axis in general, and of the cerebral 

 hemispheres in particular, were unlike the peripheral nerves 

 iuexcitable to different kinds of stimuli applied directly either to 

 the grey or to the white matter. Fritsch and Hitzig were the 

 first who demonstrated the fallacy of this belief. They found, and 

 this was their chief discovery, that a portion of the convexity of 

 the cerebral hemispheres of the dog is motor, that is, it reacts 

 by muscular movements to the direct application of a galvanic 

 current, while the other portion is iuexcitable to this stimulus. 

 On exciting with weak currents the resulting contractions are 

 limited to certain groups of muscles on the opposite side of the 



