54 



Mr. W-. H. Broadbent on the Structure [June 17, 



but some would go to the tip ; followed forwards, they spread out into a 

 thin fan, and pass to the various points already indicated. 



By repetition of this process the temporo-sphenoidal lobe will be 

 exhausted, with the exception of a considerable lamina of fibres from the 

 posterior part of the inframarginal gyrus, which passes backwards and 

 inwards to the end of the fissure of Sylvius, round which it curves into the 

 supramarginal gyrus, and another large band from the posterior end of the 

 parallel gyrus, which curves upwards and turns forwards in the axis of the 

 parietal lobe close behind the fibres which curve upwards from the corpus 

 callosum to the margin of the longitudinal fissure. 



It should be added that large bands of fibres run obliquely backwards in 

 the parallel gyrus to the bottom of the sulcus of the same name, under 

 which they turn to the inframarginal gyrus. When these are removed, the 

 deep parallel sulcus is converted into a deep narrow valley. 



The fasciculus uncinatus, in the dissection just described, has been seen 

 to receive fibres from the occipital extremity of the hemisphere, and from 

 various convolutions along its outer side, occipital, annectent, angular, 

 parallel, and inframarginal ; fibres are traceable into it also from the 

 internal grey nucleus, these mostly lying beneath those from the convolu- 

 tions, and it is probable that a few fibres from the thalamus and splenium 

 find their way into it. As it emerges from under the temporo-sphenoidal 

 lobe to cross the entrance to the fissure of Sylvius, it receives a considerable 

 contribution from the overhanging apex of this lobe, and some from the 

 uncinate lobule. Its general direction is forwards ; but a superficial set of 

 fibrse mainly from the apex of the temporo-sphenoidal lobe, passes inward 

 as well as forwards, and spreads out mainly to the edge of the longitudinal 

 fissure, passing under the olfactory sulcus ; another lamina appears from 

 beneath the edge of this, having a still more transverse direction, and its 

 fibres go to the rostrum corporis callosi, and to the callosal gyrus, detaching 

 the pointed origin of this convolution from the anterior perforated space. 

 The fibres passing directly forwards spread out under the orbital convolu- 

 tions to end in the grey matter around the edge of this lobule, some of the 

 more superficial turning into one or two of the gyri at its posterior and 

 outer margin. Deeper fibres run outwards as well as forwards, beneath the 

 convolutions of the island of Reil to the posterior part of the inferior 

 frontal gyrus ; this is a tract of considerable size. 



The convolutions of the orbitar lobule being entirely superficial to the 

 radiating fibres of the fasciculus uncinatus, must be added to those on the 

 under surface of the temporo-sphenoidal lobe as belonging to the class 

 which have no direct central communications. 



To this class also must be added, with a reservation to be noted presently, 

 the gyri operti of the island. The summit and the anterior convolutions 

 rest upon the part of the F. uncinatus which passes to the outer corner of 

 the orbitar lobule and the third frontal gyrus, and the fibres arising in the 

 grey matter of this portion of the island curve forwards across the fissure to 



