698 THE CEREBRAL CORTEX. 



motor functions of the organs designated. 1 Thus those portions, such as the 

 spinal cord and bulb and its immediate prolongations, upon which the 

 performance of simple reflex actions, unattended necessarily by consciousness, 

 depend, are regarded as forming the first or lowest level ; above these come the 

 centres, the action of which is more complex, and, in the first instance at least, 

 volitional, and necessarily attended or preceded by conscious sensations ; these 

 centres form the second level ; the third or highest level of Hughlings 

 Jackson is that part of the central nervous system which is conceived to be 

 the seat of memory and ideation. But however probable, it has not yet been 

 proved that the domicile of the highest functions is anatomically separate from 

 that of the functions with which the second level is concerned. Both are 

 unquestionably dependent, in man at least, upon the integrity of the cortex, 

 and it is very uncertain whether any special region of the cortex (e.g. the 

 frontal lobe, as Hughlings Jackson supposes to be the case) is especially 

 associated with the functions ascribed to his " highest level." This subject 

 will be further discussed later. 



The Eesults of Kemoval of both Cerebral Hemispheres. 



The results of experimental removal or destruction of the whole 

 cerebrum in animals vary according to the kind of animal and its 

 position in the scale of organisation. These results, as they have been 

 described by various physiologists, and especially by Fiourens and 

 Goltz, have been so excellently summarised by Ferrier 2 that no apology 

 is needed for quoting part of his description at length : — " Deprived of 

 its cerebral hemispheres " (the corpora striata and optic thalami being 

 included in the removal), " the frog 3 will maintain its normal attitude, and 

 resists all attempts to displace its equilibrium. If laid on its back it will 

 immediately turn on its face, and regain its station on its feet. If 

 placed on a board, and the board be tilted in any direction, the animal 

 will make the appropriate movements to throw its centre of gravity 

 within the base of support. If its foot be pinched, it will hop away. 

 If it is thrown into the water, it will swim until it reaches the side of 

 the vessel, and then clamber up and sit perfectly quiet. 4 If its back be 

 stroked gently, it will utter loud croaks, and this with such uniformity 

 on each application of the stimulus, that, as Goltz indicates, a chorus of 

 brainless frogs might be obtained which would utter their (3ps-/.r/.s>iiZ, 

 ■/.od% Mat, on the appropriate occasion in a manner which would have 

 delighted the heart of Aristophanes. 5 Indeed, in many respects, it 

 would be difficult to say that the removal of the hemispheres had 

 caused any alteration in the usual behaviour of the animal. If placed 

 in a vessel of water, the temperature of which is gradually raised, it 

 will not quietly submit to be boiled like a frog which has only its 

 medulla and spinal cord, but will leap out as soon as the bath becomes 

 uncomfortably hot. If placed at the bottom of a pail of water, it will 



1 Hughlings Jackson, " On the Relations of Different Divisions of the Nervous System 

 to one another and to Parts of the Body," Brit. Med. Journ., London, 1898, vol. i. p. 65. 



2 " Functions of the Brain," second edition, 1886, p. 109. 



3 Goltz, " Beitr. z. Lehre v. d. Functionen der Nerven centre n des Frosches," Berlin, 

 1869. 



4 But if lowered gently into the water it will remain motionless (Onimus, Journ. de 

 Vanat. et physiol. etc., Paris, 1870, p. 633; Eckhard, Hermann's " Handbuch," 1879, 

 Bd. ii. Th. 2, S. 117 ; Goltz, loc. tit.). 



5 The uniformity of this reflex is greater after removal of the thalamus than if the hemi- 

 spheres and corpora striata only are removed (Goltz, loc. cit. ; Paton, Eclin. Med. and' Sun/. 

 Journ., 1846, vol. lxvi. p. 251). If another part of the skin be simultaneously and 

 sufficiently stimulated, the reflex, as is the case with many others, is inhibited. 



