772 THE CEREBRAL CORTEX. 



not productive of paralysis nor of any actual loss of sense, yet leads to 

 inability to appreciate the impressions which are received through the 

 sense organs, to loss of memory, and to a diminution of the intellectual 

 faculties. 1 It has often been supposed that the frontal lobe is the 

 special seat of the intellectual faculties ; 2 chiefly on the ground that this 

 lobe at least the non-excitable anterior part (pre-frontal) is much 

 more developed in man than in the lower animals. But this is also true 

 for the region which Flechsig terms the parieto-occipito-temporal associa- 

 tion area ; 3 and although cases in man are cited of lesions of the frontal 

 lobes which have been followed by considerable mental and intellectual 

 disturbance, this is equally a consequence of extensive lesions, especially 

 bilateral lesions, of any part of the cortex. It is in fact more easy to 

 produce a condition of semi-idiocy in monkeys from extensive bilateral 

 lesions of the temporal lobes, than from complete severance of the pre- 

 frontal region ; an operation which may indeed be effected without 

 producing any very obvious symptoms. 4 



It is important, in effecting an extensive lesion of any part of the brain, to 

 avoid if possible removing the cerebral substance, or interfering more than 

 - can be helped with its vascular connections. It is sufficient to cut off the part 

 to be removed by a subcortical incision, so as completely to sever all its nervous 

 connections with the rest of the brain, leaving the piece thus isolated in situ. 

 In this manner much of the shock of the operation, and the mechanical and 

 vascular disturbance of the whole hemisphere, which results from entire 

 removal of a large piece of brain, and which may lead to erroneous conclusions 

 being arrived at, 5 are in some measure avoided. Operating in this way, I have 

 in several cases completely removed in the monkey the whole of the in excitable 

 area of both frontal lobes without producing the slightest sign of the mental 

 and intellectual dulness and alteration of character which has been regarded as 

 pathognomonic of a lesion of this region. 6 Many cases have also been 

 described in man in which lesions of the frontal lobes have not been followed 

 by any marked symptoms of this kind, and, on the other hand, they are apt to 

 supervene with extensive bilateral lesions of other parts of the cortex. 7 



So much has been made of certain clinical cases in which an extensive 

 lesion of the frontal lobes was followed by diminution of the intellectual 



1 For a criticism of Flechsig's views see Dejerine, Compt. rend. Soc. de biol., Paris, 

 1897, p. 178, who insists that numerous fibres pass from all parts of the cortex to the basal 

 ganglia, or, in other words, that the association areas of Flechsig are in fact also projection 

 areas. It must not be overlooked that the association of action of different parts of 

 the cerebral cortex may equally well be carried out through fibres passing vertically in 

 the corona radiata to and from the thalamus as by fibres passing tangentially from one 

 portion of the cortex to another. 



2 See below. 



3 The parietal lobe, rather than the frontal, has been especially found to be developed 

 in some men of genius. This has been the case with great musicians, such as Bach and 

 Beethoven, and also with men eminent in science and philosophy, such as Dbllinger, Gauss, 

 Liebig, and Kant (cf. Riidinger, " Ein Beitr. z. Anat. d. Affenspalte, u.s.w.," Bonn, 1882). 



4 Horsley and Schafer, Phil. Trans., London, 1888, B ; Schafer, Trans. Internat. Cong. 

 Psychol., London, 1893. 



5 Ferrier and Turner, for example, obtained on extirpation of the left frontal lobe in 

 front of the precentral sulcus, deviation of both eyes to the left, paresis of the right arm 

 and leg, left hemiopia and impairment of cutaneous sensibility over the whole of the right 

 side, a dull, sleepy condition being also observed (Phil. Trans., London, 1898, B, p. 365). 

 It is impossible to suppose that all the functions which were impaired by the lesion had 

 their seat in this lobe. 



6 Compare with these the results obtained by Bianchi, see Brain, London, 1895, vol. 

 xviii. p. 498 ; also Grosglick, Arch. f. Physiol., Leipzig, 1895, S. 98. Such examples of a 

 markedly contrary result are probably due to neglect of the above-mentioned considerations. 



7 Cf. Bruns, Neurol. Ccntralbl., Leipzig, 1898, S. 770, 848 ; Williamson, Brain, London, 

 1896, vol. xix. p. 346; Bernhardt, "Symptomalogie u. Diagnostik der Hirngeschwulste," 

 Berlin, 1881 ; Oppenheim, "Die Geschwiilste des Gehirns," Wien, 1896. 



