544 



THE CEREBRUM. 



thalamus, which appears in its cavity and forms its anterior boundary, 

 while its remaining boundaries are formed by the hemisphere. At its com- 

 mencement it is directed backwards and outwards ; then, passing downwards 

 with a sweep, it curves forwards, and at its extremity has a marked inclina- 

 tion inwards. The principal object seen upon the floor of this cornu is the 

 hippocampus major (pes hippocampi, or cornu ammonis), a large white 

 eminence extending the whole length of the cornu. The hippocampus 

 major becomes enlarged towards its anterior and lower extremity, and is 

 indented or notched on its edge, so as to present some resemblance to the 

 'paw of an animal, whence, no doubt, its name of pes hippocampi. The 

 white fibres of its surface are directed obliquely backwards and outwards 

 across it: they form only a thin smooth layer, and beneath them is cineritious 

 matter continuous with that of the surface of the hemisphere. Along the 

 inner edge of this eminence is seen a narrow white band, named corpus 

 fimbriatum or tcenia hippocampi, which is prolonged from the fornix ; to the 

 inner side of the tsenia is a part of the choroid plexus, and next to that the 

 back of the optic thalamus. This cornu differs from the others in respect 

 that it is not a mere cul-de-sac, but, by the mere separation of the mem- 

 branes, can be made to communicate in its whole length with the surface 

 of the brain by the fissure through which the choroid plexus enters. 



Fig. 372. 



Fig. 372. A DEEP VIEW OP 

 THE LATERAL VENTRICLES 

 AND THEIR CoRNUA WITH THR 

 VELUM INTERPOSITUM. | 



The fornix has heen divided 

 near its anterior pillars and 

 turned back, c, the anterior 

 part of the corpus callosum 

 divided; e, the lyra on the 

 lower surface of the corpus 

 callosum and fornix ; /, ante- 

 rior pillars of the fornix divided 

 (these are represented of too 

 large a size) ; g, anterior, and 

 7t, posterior cornu of the lateral 

 ventricle ; k, k, corpora striata; 

 , pes hippocampi in the lower 

 part of the middle cornu ; r, r t 

 thalami optici ; s, , tsenia se- 

 micircularis ; t, t, choroid 

 plexus ; v, velum interpositum; 

 a:, x, posterior pillars of the 

 fornix ; y t emiuentia collate- 

 ralis. 



The posterior cornu pro- 

 jects backwards into the 

 substance of the posterior 

 lobe. At its extremity it 



is pointed, and directed inwards. On the inner side of its floor is a curved 

 and pointed longitudinal eminence, named hippocampus minor, ergot, or 

 calcar avis ; and at the junction of the posterior with the descending cornu, 

 between the hippocampus major and minor, is a smooth eminence, named 

 eminentia collateralis, or pes accessorius. 



The hippocampus minor is only the convex side of the fold which forms 

 the calcarine sulcus, and part of the sulcus of the hippocampi ; and in like 



