THE A UD1T0R Y AREA. 7 6 1 



conductivity in the optic tract led to partial colour blindness, combined with a 

 diminution of the power of appreciating the relative intensity of light, and 

 interprets this observation as indicating the non-existence of a separate centre 

 for colour appreciation. This interpretation cannot, however, be conceded, for 

 the results may be explained by assuming that the nervous impulses for these 

 qualities are conducted along different nerve fibres, which are differently 

 affected by the conditions disturbing their conductivity — a phenomenon well 

 known to occur in other mixed nerves. There is not sufficient evidence as yet 

 to enable an authoritative opinion to be pronounced upon this matter. It has 

 been suggested that the fact that in unilateral lesions of the cortex central 

 vision is often unaffected, may be explained by supposing that the vascular 

 conditions of the part of the cortex which is connected with the macula are 

 more favourable, so that this particular portion of the centre is more resistant to 

 pathological changes than the rest, without the necessity of assuming that the 

 whole macula is represented upon both sides of the brain, but there is no 

 evidence in favour of this suggestion. 1 



The auditory area of the cerebral cortex. — -It was originally stated 

 by Ferrier, 2 and the statement has been confirmed by all subsequent 

 observers, that stimulation in the monkey of the upper two-thirds of the 

 inferior temporal convolution causes pricking of the opposite ear, turning 

 of the head and eyes to the opposite side, and dilatation of the pupils. 3 

 This was taken by Ferrier to indicate that this convolution is connected 

 with the function of hearing (by the opposite ear), and in conformity 

 with this view he found that if it was destroyed on one side, and the ear 

 of the same side was stopped with wax, the animal was rendered deaf ; 

 and that if it was destroyed on both sides the animal became absolutely 

 and permanently deaf. Ferrier therefore concluded that this gyrus, and 

 this alone, is the cerebral seat of the auditory function. 



I have elsewhere, however, shown that this deduction of Ferrier was 

 founded upon an insufficient basis. 4 On repeating his experiments, in 

 conjunction with Sanger Brown, it was found that monkeys entirely 

 deprived of the superior temporal gyri on both sides, and even of a very 

 considerable additional amount of the temporal lobe, are by no means 

 deaf, but still show signs of hearing quite distinctly, and of understanding 

 the nature of the sounds heard/' Even in the case upon which Ferrier 

 chiefly relied in support of his opinion, the notes which he has published 

 show that the monkey undoubtedly reacted to sounds. 6 



It is certain, therefore, that the function of sound-perception is not 

 entirely localised to the superior temporal gyrus, although the focal 

 point for it is probably there. Luciani and Tamburini 7 extended it to 

 the second temporal gyrus, because excitation of the upper end of this 

 also gives the head- and eye-movement. H. Munk, chiefly from experi- 

 ments on dogs, 8 ascribes the function to the whole of the temporal lobe. 

 Luciani, 9 in a later communication, says : " Our results tend to show 



1 W. Harris, Brain, London, 1897, p.*307. - Proc. Boy. Soc. London, 1875. 



3 I have myself generally got retraction of the car instead of pricking. Baginsky (with 

 H. Munk) obtained raising of eyelids combined with movements of the opposite ear on stimu- 

 lating the lowermost point of the temporal lobe in the dog (Neurol. CrntralbL, Leipzig, 

 1890, Bd. ix. S. 458). Steiner {op. cit.) in the rabbit also obtained movement of the 

 opposite ear, on excitation of the same part of the temporal lobe. 



4 Brain, London, 1888, vol. x. p. 362. 



5 Sanger Brown and Schafer, Phil. Trans., London, 1888, B., p. 303. 



6 Brain, London, 1888, vol. xi. p. 14 ct seq. 



7 "Sulle funzione del cervello ; seconda comniunicazione," 1879. 



8 Gcs. Abhandl., Mitth. 4, S. 63. 



u "On Sensorial Localisations," etc., Brain, London, 1884, vol. vii. p. 195. 



