SENSOR Y AREAS IN THE MONKE Y AND MAN. 749 



defects of speech, do not produce actual paralysis of the organs of speech 

 (larynx, tongue, etc.). 1 



THE SENSORY AREAS OF THE CEREBRAL CORTEX IN THE MONKEY 



AND MAN. 



Besides the areas which have just been described, it is found that 

 excitation of certain other regions of the surface of the hemisphere 

 also produces definite movements. Thus, excitation of the superior 

 temporal convolution of the monkey causes the animal to turn its 

 head and eyes to the opposite side and to prick its ear, 2 and a 

 similar movement of the head and eyes is provoked by stimulation of 

 the posterior part of the hemisphere. Terrier also obtained " torsion of 

 the lip and semiclosure of the nostril on the same side," when he excited 

 a small area on the anterior and inner aspect of the uncinate gyrus ; and 

 he further states that sometimes, on exciting the lower extremity of the 

 middle temporal convolution, " movements of the tongue, cheek-pouches, 

 and jaws were induced, very like those which are characteristic of 

 tasting." 



Extirpation of the above areas is not, however, in any case followed 

 by motor paresis, nor does there occur any long descending degeneration, 

 like that down the pyramidal tract, as is always the case with a lesion 

 of the excitable part of the parietal and frontal regions. On the other 

 hand, there is indubitable evidence at least in the case of the occipital 

 region that extirpation or lesion is productive of marked and per- 

 manent sensory disturbance (hemiopia). It has therefore been assumed 

 by Ferrier and others, probably with reason, that in this case the move- 

 ments which are produced are the result of and secondary to ideas of 

 sensation which are called up by the stimulation, and it is inferred 

 that the areas in question at least those which have been most fully 

 investigated are portions of the cortex which are connected with the 

 perception of, and response to, sensations derived from the organs of 

 special sense, and differ in their mode of action from the " motor " areas 

 by producing the movements in question in a more indirect manner. 

 Other neurologists, on the other hand, have taken up the position that 

 in all cases, whether the excitation is applied to the Kolandic or to the 

 other areas, the movement produced is the result of subjective sensations, 

 or ideas evoked by the excitation ; by some it has been held that, in the 

 case of the Rolandic area, the sensation thus excited is the sense of 

 movement or muscular sense. If the result is brought about in a 

 similar manner, the period of latent excitation of the muscles which 

 are set in action should be about the same in both cases, whereas, 

 if in the one case the transmission of impulses is more direct, there 



1 Amongst papers dealing with the subject of the localisation of motor centres in man, 

 the following may be cited, in addition to those already referred to : Seguin, Trails. 

 Am. Neurol. Assoc., N. Y., 1877 ; Journ. New. and Ment. Dis., N. Y., 1881 ; Gowers, 

 Brain, London, 1878, vol. i. p. 388 (congenital absence of hand, associated with atrophy 

 of middle part of ascending parietal) ; Bastian and Horsley, JBrain, London, 1880, vol. iii. 

 p. 113 (a similar case to the above); Exner, "Local, d. Funct. in d. Grosshirnr. d. 

 Menschen," Wien, 1881 ; and in Hermann's "Handbuch," 1879, Bd. ii. ; Starr, "Local- 

 ised Cerebral Disease," Am. Journ. Med. Sc., Phila., 1884 ; Keen, Am. Journ. Med. Sc., 

 Phila., November 1888; Phila. Med. News, 1890, p. 381; Ferrier, "Cerebral Localisa- 

 tion," 1890 ; M'Bride, Journ. Nero, and Ment. Dis., N. Y., 1890, vol. vii. p. 512 ; C. K. 

 Mills, Brain, London, 1899, vol. xii. pp. 233, 358. 



2 Ferrier, Proc. Roy. Soc. London, 1875, vol. xxiii. p. 426. 



