'////: c Kit KB HUM. ;:.-, 



an. I divides into t\vo cords or <mt'-r!<-r pillars (crura) (Fig. 323, 17), which 



in front of the anterior cerebral commissure, are inflected downwards 



and buck wanls. in traversing the optic thalamus, on the sides of the mid. 11.; 



ventricle, and. finally, have their extremities confounded with the mammillary 



rj'iix albicans). 

 Tli' - f.vo crura limit, in front, tlic foramen comma m' <ni/',-i".i or foramen 



. over which the apex of the foriiix is thrown across like an arch. 

 The t'ornix is white throughout its whole extent, with a greyish tint 

 towards its summit. 



5. The Hippocampi. (Fig. 331, 4.) 



The Jiijipoi-iniipus or cornu Ammonia (from its resemhlance to a ram's 

 horn, the crest of Jupiter Ammou), is an elongated projection, a veritable 

 internal convolution of the brain (is, in fact, the internal surface of the 

 gyrus furmcutus or convolution lying upon the corpus callosum, and which 

 terminates at the fissure of Sylvius) ; it occupies the floor of the anterior 

 u of the lateral ventricle, and is prolonged throughout its reflected por- 

 tion, whose curvature it exactly follows. Considered together, the two 

 hippocampi somewhat closely resemble the uterine corutia of the Cow. 



By their internal extremity, they are in contact with each other beneath 



the middle portion of the fornix, and above the optic thalamus, wbich is sepa- 



i from them by the velum iuterpositum (Fig. 327, 9). Their external 



mity occupies, in the mastoid lobule, the cul-de-sac of the reflected 



portion of the lateral ventricle. 



The central mass of this projection is formed by a nucleus of grey sub- 

 stance, covered superficially by a cortical layer of white a prolongation of 

 the posterior crura of the fornix. 



Towards the concave border of the hippocampus, this white lamina 



offers a kind of wide hem, beneath which the choroid plexus passes ; this 



hem constitutes a small curved band, like the cornu Ammonis, wider at its 



middle part than at its extremities, and is named the corpus fimbriatum, or 



pus. 



6. The Corpora Striata. (Fig. 331, 7.) 



The corpus striatnm is another projection on the floor of the cerebral 

 vein ipymg the anterior region of that cavity. 



This eminence is pyrifonn in shape, and obliquely elongated from behind 



' >re, and without to within. Its surface is smooth, and regularly convex. 



Its base, or anterior extremity, corresponds to the anterior caecum of the 



>le. Tin- summit, or posterior extremity, disappears at the commence- 



of the ! fleeted portion of the ventricular cavity. Outwardly, the 



:s Ktriatum is limited by a groove that forms the angle of union between 



!<>or and roof of the ventricle. Inwardly, it is separated from the optic 



thalamus and cornu Ammonis by another sulcus, in which the choroid 



plexus floats, and which is oblique inwards and forwards, and shows at the 



.1 the tcenia eemicircularin (Fig. 323, 13). This is a flattened white 



cord. \sbicli disappears inwardly towards the foramen of Monro, and bends 



; d> along the optic nerve to within about 3-8ths of an inch from the 



in this way forming a sort of circular band around the anterior 



iiiity of the isthmus, beneath which all the fibres of the latter pass to 



n ;ieh tl,. cen-bral hemispheres. 



The corpus Ktriatum owes its name to its structure, being composed of a 



