458 THE INTERNAL STRUCTURE 



siderable group of them also proceeds to the tip of the Temporal 

 Lobe. 



3. Other inferior and more superficial longitudinal fibres pass 

 from the tip of the Temporal Lobe backwards (diverging as they 

 go) into the floor of the ' descending corrni ' and into that of the 

 posterior cornu, where they become mixed with fibres of the Corpus 

 Callosum. 



4. The Convolutions on the flat internal surface of the hemi- 

 sphere, especially the ' gyrus fornicatus,' contain longitudinal fibres, 

 These latter are said to extend from the 'anterior perforated space f 

 in front (Corpus Striatum) backwards over the Corpus Callosum, 

 round its posterior extremity, and thence, according to Foville, 

 onwards to the tip of the Temporal Lobe. 



5. Certain longitudinal fibres ('nerves of Lancisi') are situated 

 on the upper surface of the Corpus Callosum in two series on each 

 side (fig. 163). In front they also are said to come into relation 

 with the 'anterior perforated space,' whilst posteriorly their des- 

 tination is doubtful. According to Foville they join the ' posterior 

 pillars ' of the Fornix.* 



Other sets of ' commissural fibres ' are not so distinctly 

 longitudinal in direction, and they serve, moreover, to 

 bring more immediately adjacent Convolutions into rela- 

 tion with one another. 



We still possess a very inadequate knowledge of these 

 multitudinous sets of fibres, but it would be quite impos- 

 sible here to attempt to render an account of all that has 

 been made out in regard to them. A few illustrations of 

 the best marked of these connections may, however, be 

 given in order to convey some idea of the extent of inter- 

 relation existing between contiguous Convolutions. 



Broadbent says f : " The second or great ascending parietal 



* These last two sets of fibres may therefore possibly pass by 

 circuitous routes from ' sensory ' regions in the Temporal Lobe to 

 the corresponding Corpus Striatum. Other regions of this Lobe 

 seem to be connected with the same body in a much more direct 

 manner, i.e., by fibres which cross the Sylvian fissure (p. 445). 



f Loc. cit. p. 11. 



