7o6 THE CEREBRAL CORTEX. 



This was the condition of the subject when, in 1870, were published 

 the experiments of Fritsch and Hitzig, 1 which clearly showed that the 

 doctrine of the non-excitability of the cortex was erroneous. Fritsch 

 and Hitzig found that electrical excitation of the dog's brain, at certain 

 definite points upon the convolutions in the immediate neighbourhood 

 of the crucial sulcus, is responded to by movement of parts on the 

 opposite side of the body, that more prolonged stimulation produces 

 local convulsive movements of the same parts, which may be followed 

 by general epileptiform convulsions, and that removal of the localised 

 brain area is followed by paralytic symptoms in the parts of the body 

 or in the limbs which had previously responded to their excitation. 

 From these experiments it became obvious (1) That parts of the 

 cerebral cortex can be directly excited to action by artificial stimulation ; 



(2) that excitation of similar points in different animals, or upon 

 opposite sides of the brain of the same animal, produces similar results ; 



(3) that many parts of the cortex are apparently not thus directly 

 excitable ; (4) that the movements produced by artificial excitation are 

 similar in their general character to those which are the result of 

 voluntary movements of the animal ; (5) that the voluntary movements 

 of the opposite side of the body are interfered with on removal of the 

 excitable areas upon one side of the brain. 



These facts, which were established by Fritsch and Hitzig by 

 their experiments upon the dog's brain, were verified and amplified 

 by those of Ferrier 2 upon the brain both of the dog and monkey, 

 and of many other mammals, and they have been abundantly tested 

 and found to hold good for the human brain, in cases where by 

 accident, disease, or the necessity of operation, the cortex has been 

 laid bare. 



Although it is difficult to obtain the movements in question by 

 mechanical or chemical excitation, yet it is possible under some 

 circumstances to do so; 3 and, as already stated, similar effects are 

 obtained as the result of irritative lesions of the cerebral surface in man 

 (Jacksonian epilepsy). 



It was shown by Burdon Sanderson 4 that if the cortex cerebri be removed 

 at one of the excitable points, and the stimulating electrodes be placed upon 

 the cut ends of the subjacent fibres of the corona radiata, a movement 

 is evoked which is of a character precisely similar to that which had been 

 previously called forth by excitation of the superjacent cortex itself. 5 In 

 non-narcotised animals the cortex is more excitable than the subjacent corona 

 radiata, whereas in narcotised animals the reverse is the case. 6 The brain 

 of new-born dogs does not yield results on stimulation, but animals which 

 are born in a more mature state, e.g. guinea-pigs, give cortical reactions. In 

 the dog the eifects of excitation begin to show themselves about the tenth 



1 "Ueber die elektrische Erregbarkeit des Grosshirns, " Arch. f. Anat., Physiol. u. 

 wissensch. Afcd., 1870, S. 300. 



2 West Riding Lun. Asyl. Rep., London, 1873; Proc. Hoy. Soc. London, 1874, vol. xxii. 

 p. 229 ; 1875, vol. xxiii. p. 409 ; "Functions of the Brain," 1876. 



3 Fransois-Franck and Pitres, Progrts mtd. , Paris, Jan. 5, 1878 ; Landois, Wien. med. 

 Prex*e, 1887, Nos. 7-9. 



4 Proc. Roy. Soc. London, 1874, vol. xxii. p. 368. 



5 Cf. also Braun, in Beitr. z. Anat. u. Physiol. (Eckhard), Giessen, 1874, Bd. vii. S. 2 ; 

 and Putnam, Boston Med. and S. Journ., 1874, vol. xci. p. 49. 



6 Richet, "Diet, de physiol.," tome iii. p. 2, art. "Cerveau." See on this and various 

 other points connected with the subject of cortical excitation in the dog, Francois-Franck, 

 "Le9ons sur les fonctions motrices du cerveau," Paris, 1887. 



