73 2 



THE CEREBRAL CORTEX. 



Detailed Kesults of Stimulating the Motor Cortex in Animals. 



The results which were obtained by Fritsch and Hitzig (Fig. 331) 

 in the dog have already been alluded to. Their experiments showed 

 that there are certain definite points or centres, mostly situated on 

 the convolution bounding the crucial sulcus — stimulation of which 

 constantly produces (a) movements of the head (contraction of neck- 

 muscles) ; (b) of the opposite forearm, extension and adduction ; and, 

 at an adjacent point, flexion and rotation (? supination) ; (c) of the 

 opposite hind-leg ; (d) of the facial muscles and eyes. They also ob- 

 tained from intermediate but less circumscribed points contractions 



of the muscles of the back, tail and 

 abdomen. 



Many other physiologists 1 have 

 confirmed and extended the observa- 

 tions of Fritsch and Hitzig upon the 

 dog. Ferrier was one of the first, 

 and his results, which were obtained 

 by an improved method, that of fara- 

 dic excitation (whereas Fritsch and 

 Hitzig employed for the most part 

 the galvanic current), were on the 

 whole confirmatory of those of the 

 two German observers, which they 

 materially extended. They are em- 

 bodied in the accompanying diagram, 

 to the explanation of which the 

 reader is referred. Ferrier obtained 

 similar results in the jackal, and with 

 slight modifications in the cat (Fig. 

 333). In rodents (rabbit, guinea-pig, 

 rat), in which the hemispheres are 

 smooth, stimulation of certain points 

 of the external surface, in front of 

 and above the fissure of Sylvius, gave 

 the results which are shown in Fig. 

 334, and very similar results have 

 been arrived at for insectivora, 2 for marsupials, 3 and for monotremes. 4 

 In birds only a single limited region at the vertex of the hemisphere 

 was found by Ferrier to be responsive to excitation, and this 

 caused contraction of the opposite pupil, occasionally associated with 

 turning of the head to the opposite side. 5 In the frog 6 and fish, 7 



1 Ferrier, Proc. Ray. Soc. London, 1874; "Functions of the Brain," London, 1876; 

 Luciani and Tamburini, "Rich. s. centri psicomotori corticali," Reggio-Emilia, 1878-79, 

 noticed in Brain, London, 1879, vol. i. p. 529, and vol. ii. p. 234 ; H. Mmik, Ges. 

 Abhandl., Berlin, 1890 ; Francois-Franck and Pitres, various papers, the results of 

 which are given by Franck in "Lecons sur les fonctions motrices du cerveau," Paris, 

 1887, p. 7. 



" G. Mann, Journ. Anat. and Physiol., London, 1895, vol. xxx. p. 1. 



3 Ziehen, Centralbl. f. Physiol., Leipzig u. Wien, 1897, Bd. xi. S. 457. 



4 C. J. Martin, Journ. Physiol., Cambridge and London, 1898, vol. xxiii. p. 383. 



5 Wesley Mills (Brit. Med. Journ., London, 1897, vol. ii. p. 1485) and Boyce 

 (communication to Congress of Physiology at Cambridge, 1898) have succeeded in 

 obtaining other movements of the head in birds. 



6 Ferrier, loc. tit. ; Langendorff, Centralbl. f. d. mcd. Wisscnsch., Berlin, 1876, S. 945. 



7 Ferrier, loc. tit. 



Fiu. 331. — Diagram showing the chief 

 results obtained by Fritsch and Hitzig 

 (in 1870), on stimulation of the cerebral 

 cortex of the dog. (a) Contraction of 

 neck muscles ; (b) of arm muscles ; (c) of 

 leg muscles ; (d) of facial muscles and 

 eye movements. 



