158 



Temporal Lobe and Auditory Areas 



[CHAP. 



In the inner or central direction the area comes to a point where the transverse 

 temporal gyri converge, and the important point is noticed that the arrangement does not 

 show any indication of ascending the parietal operculum. 



It is difficult to give a clear diagrammatic representation of the distribution of this 

 type of arrangement, but in the accompanying figure, the area has been transferred to a 

 brain in which the Sylvian fissure has been opened out. 



Lower Border of Sylvius 



FIG. 15. Drawing of left cerebral hemisphere (human) with Sylvian fissure opened out. 



Showing (1) the audito-sensory area (shaded) confined to the two transverse temporal gyri and not extending on to the 

 insula ; (2) the audito-psychic area (large clots) on the free surface of the posterior three-fifths of the first temporal 

 gyrus ; (3) the extent, on the lateral surface of the hemisphere, of the common temporal cortex (small dots). 

 S. C. /. = sulcus centralis insulae ; R. H. 8. =ramus horizontalis Sylvii ; R. A. S. = ramus ascendens Sylvii ; Free. 

 Jn/. = suleus precentralis inferior; P. 0. = parieto-occipital fissure; R. 0. r. = ramus occipitalis transversus; T. II. = 

 sulcus temporalis secundus. 



Type II. Coming next to the area over which cortex showing an intermediate degree 

 of fibre-wealth is distributed, this is soon described as it forms a broad skirt or margin to 

 the concealed area above-mentioned. It is also almost entirely confined to the first temporal 

 convolution. 



I cannot indicate its anterior limit on the free surface better than by saying that it 

 corresponds to the point where an imaginary line made continuous with the lower extremity 

 of the fissure of Rolando would cross the temporal lobe, but I should add that this line 

 of demarcation is not a sharp one. 



Interiorly, the first temporal sulcus forms a good boundary, and I must not forget to 

 mention that transverse sections show that this type of arrangement does not extend more 

 than about half-way down the upper wall of the sulcus. 



In the posterior direction the area tends to broaden slightly, and it might either be 

 described as investing the downward prolongation of the fissure of Sylvius, or as being 



