vi] Siiiini/tiri/ <in</ CoiichixiiHix 169 



time there is some lack of unanimity <>n this point. By another long band of fibres, the 

 fasciculus longitudinalis superior, which has also been previously mentioned, the superior 

 temporal gyms is supposed to have connections with the insula and the inferior frontal 

 convolution. Other fibres are said to pass to the opposite hemisphere, by way of the 

 corpus callosum, and connect the auditory areas of the two sides; and lastly sets of short 

 autochthonous neurones serve to bring different parts of the auditory area into relation, 

 while others proceed to gyri in the immediate neighbourhood. But in the words of Barker, 

 who has collected all the available data on these neurones, " a vast deal of research will be 

 required before very definite statements concerning them can be made." 



Coxn.rsioxs AND CONSIDERATIONS. 



The first and perhaps the most firmly-grounded conclusion derived from this research 

 is, that the area of cortex laid down lor the primary reception of simple auditory stimuli 

 is that which I have mapped out and described as mainly covering the transverse temporal 

 gyri of Heschl. 



The reasons for this conclusion are as follows: (1) Microscopic examination proves that 

 the area possesses a type of histological structure entirely different from that of any other 

 part of the temporal lobe; not only so, the type of arrangement of rnedullated nerve fibres 

 is peculiar inasmuch as the fibres of large calibre, which are present in great abundance, 

 have the appearance which has been noted elsewhere as characteristic of corticipetal fibres ; 

 that is to say, instead of descending in the radiary fasciculi and striking the white 

 substance more or less at a right angle, they seem to issue from the white substance at 

 an acute angle and then cross obliquely for some distance in the radiary zone, as if seeking 

 one of the large nerve cells which constitute another distinguishing feature of this area. 

 To these fibres therefore I attach great importance. 



( 2 ) If the area mapped out on embryological lines by Flechsig be compared with that 

 which I have defined independently by an examination of the adult cortex, it will be found 

 that the outlines of the two fields exhibit a singular agreement, an agreement which must 

 be regarded as more than accidental ; the reason why such a correspondence should exist 

 is not far to seek, for, as we all know, Flechsig s aiva was determined by noting the field 

 of impact of strands of fibres, which are of early development, and in suitable fetal brains 

 may be seen streaming out from the median geniculate bodies and posterior corpora 

 quadrigemina, and traversing the white substance in the direction of this special field 

 of cortex. 



Judged by their developmental peculiarity, by their degenerative reactions, and by their 

 peripheral connections, there seems to be no doubt that these fibres represent the uppermost 

 link in the chain of auditory neurone's. 



It is equally probable that the fibres which I have recognised in the cortex of this 

 region, and by the presence of which it has been possible for me to map out a definite 

 area, in both the human and the anthropoid brain, are the cortical continuations of the 

 fibres which Flechsig's embryological studies have displayed. 



So that just as in the central visual apparatus we find fibres in band form, acquiring 

 their medullated sheath at an early date, restricted in their distribution to a limited area, 

 namely, the walls and lips of the calcarine fissure, an area further characterised by the 



c. 22 



