THE CEREBRUM. 365 



conceals all the upper surface of the thalami except their exter- 

 nal margins, and, having reached their anterior extremities, its 

 apex descends towards the basis of the brain. 



The body of the fornix is about a line thick, but, at its ante- 

 rior extremity, it becomes somewhat cylindrical, and is divided 

 into two columns, called Crura Fornicis Anteriora. Each of 

 these crura, in descending adheres to the anterior extremity of 

 the thalamus of that side, and, getting finally below it into the 

 floor of the third ventricle, i(, after a course slightly curved, 

 joins the cortical substance of the Eminentiae Mamrnillares. 

 Santorini, aware of this junction, considered the eminentias 

 as a part of the fornix, and, therefore, called them Bulbi For- 

 nicis. 



The fornix has other attachments of a more complex descrip- 

 tion, which the anatomist should attend to, as they serve to 

 indicate the modes of intercourse between the several parts of 

 the cerebrum. Its fibres having reached, and probably formed, 

 the eminentias mammillares, one fasciculus of them ascends 

 from thence along the internal face of the optic thalamus, in- 

 vested by the cineritious matter of the latter, and spreads it- 

 self above like a fan, and forms the tuberculum anterius: a se- 

 cond fasciculus from the same point, having divided into two, 

 after going a short distance, sends one division backwards 

 along the upper internal face of the optic thalamus, to join 

 the peduncle of the pineal gland, and the other division, which 

 is more anterior, runs to join the tasnia striata; the third fasci- 

 culus from the eminentia mammillaris, being covered by the 

 optic nerve, goes outwards and backwards to terminate in the 

 thalamus. 



The posterior margin, or the base of the fornix, besides run- 

 ning into the corpus cnllosum, has the angle on each side elon- 

 gated so as to rest upon and to join the upper end of the cornu 

 ammonis. The angle, being continued, then follows the wind- 

 ing course of the latter, adhering to its posterior margin, but 

 hanging loosely over the anterior. This loose edge or continu- 

 ation of the external margin of the fornix is the Tacnia Hippo- 

 campi, or Corpus Fimbr'iatum of the Lateral Ven;ricle. The 

 elongations of the posterior angles are called Crura Posteriora 

 Fornicis. In the brains of individuals who have suffered from 

 general dropsy, one frequently finds the fornix narrower than 



