56 



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



The hippocampus major may be briefly described as a curved groove or 

 " gutter " (Gratiolet) of fibres, the upper border of which is formed by the 

 posterior pillar of the fornix, while the lower is concealed by the gyrus 

 uncinatus, the grey matter of which folds over it into the groove, and 

 after reaching the bottom bends np the other wall for a short distance, 

 forming the plicated " C. fimbriatum," or " Pli godronne." The outer 

 surface of the case of fibres is smooth, and for the most part free in the de- 

 scending cornu ; it adheres to the inferior wall formed by the plane of 

 fibres previously described, but can easily be detached. The course of the 

 fibres forming the case or groove is from the lower edge backwards and 

 upwards round the convexity to the upper edge, where they pass into the 

 pillar of the fornix, or where the hippocampus joins the splenium, into 

 the recurved process. Further details are given in the paper itself. 



The fibres crossing the floor of the ventricle curve forward, apparently 

 towards the apex, but are too few to be followed absolutely to their 

 termination. 



From the body of the C. callosum, at its posterior part, the fibres mostly 

 radiate backwards and outwards into the cuneus and occipital lobe generally ; 

 but a considerable number on the under surface bend from the roof of the 

 ventricle down its outer wall, across the longitudinal fibres from the 

 thalamus, &c, and curve forwards in the ridge. A considerable propor- 

 tion of these has been traced to the internal grey nucleus, others seem to 

 pass forwards to the grey matter near the apex of the temporo-sphenoidal 

 lobe. 



The relations of the cms and great central ganglia may be described as 

 follows. The crus, as it plunges into the hemisphere, is encircled on its 

 inferior aspect by the optic tract ; it then expands into a large fan of 

 fibres, the edges of which are antero-posterior, the surfaces oblicpiely up- 

 wards and inwards, and downwards and outwards. The two great ganglia, 

 the C. striatum and thalamus may be said to sit astride the anterior aud 

 posterior edge respectively of the fan, each having an intra- and extraven- 

 tricular part, the C. striatum being much the larger, and situate above, as 

 well as in front of the thalamus. 



"When the optic tract is removed, the groove in which it rests is seen to 

 present fibres having the same general direction round the crus ; they 

 have been called by Gratiolet "l'anse du pedoncle," a term which may be 

 translated by the expression " the collar of the crus." The most conspi- 

 cuous part of the collar consists of fibres from the thalamus, which curve 

 forward round the crus to end in the tuber cinereum, or run up in the 

 wall of the third ventricle to the velum interpositum, &c. Within this 

 fibres are seen to turn forwards from the posterior border of both crust and 

 tegment of the crus, to end in the C. striatum, and anteriorly a consider- 

 able mass of fibres from the tegmentum curves with a bold sweep round the 

 edge of the crust, and passes backwards and outwards into this same 

 ganglion. 



