CHAPTER VI. 



TEMPORAL LOBE. 



TYPES OF FIBRE ARRANGEMENT. 



IF a vertical transverse section of the temporal convolutions, taken from about the 

 middle of the lobe, so as to include a view of the transverse temporal gyri of Heschl 1 , 

 be stained for nerve fibres and examined, it may be observed even with the naked eye 

 that the cortex presents different degrees of intensity of coloration. Beginning with the 

 cortex coating the upper surface of the superior or first temporal convolution, that is to 

 say the surface bearing the gyri of Heschl, the depth of coloration is great; passing to 

 the exposed lateral surface of the same convolution we find an obvious reduction in tone ; 

 and descending to the underlying second and third temporal convolutions we notice that 

 the pallor is still more decided. Further examination with the microscope confirms the 

 difference in structure suggested by the naked eye appearances, and in point of fact, 

 three distinct types of fibre arrangement are here represented ; of these I shall now point 

 out the distinguishing features, leaving their distribution and also an account of the co- 

 existent type of cell-lamination to another section. 



I shall begin with the cortex covering the transverse temporal gyri of Heschl. 



FIBRE ARRANGEMENT IN THE CORTEX OF THE TRANSVERSE TEMPORAL GYRI OF HESCHL. 



TYPE No. 1. 



The intense colour tone of the cortex covering these gyri is a feature which our study 

 of the cortex in other parts of the brain has taught us to associate with profound fibre 

 wealth. But although the fibre-endowment here is unquestionably great it cannot be said 

 that there is a corresponding increase in the total depth of the cortex ; this we may 



1 On that portion of the superior temporal gyms concealed within the Sylvian fissure, the surface of which looks 

 upwards and inwards towards the insula, several parallel gyri sometimes as many as five may be distinguished, 

 running from before and laterally backwards toward the middle line. They have been termed by Heschl the transverse 

 temporal gyri. Of these the most constant and best developed is the anterior. It springs from the superior 

 temporal gyrus at about the middle of the fissure of Sylvius, and the sulcus which divides it from the succeeding 

 transverse gyrus behind is often of great depth, and of such extent that it appears on the lateral surface, where it may 

 not only indent but even bisect the superior temporal gyrus. This arrangement is commoner in the left hemisphere 

 than in the right, and in males than in females. 



The anterior gyrus is distinguishable at a time when none of the other transverse gyri are recognisable, and 

 even at the beginning of the fifth month it may be seen plainly as a gentle elevation on the lower margin of 

 the still open Sylvian fissure. 



