130 



THE FORNIX. 



pillars find a termination in the grey matter of the corpora albicantia, and are not 

 directly continuous, as in dissected preparations they seem to be, with the bundle of 

 Vicq-d'Azyr. 



The posterior pillars or crura of the fornix (fig. 94, 13} are the diverging 

 posterior prolongations of the two flat lateral bands composing the body. At first 



sure ; co.m, middle commissure ; c/i, chiasma 

 quadrigemina ; ay, aqueduct. 



Fig. 93. SKETCH SHOWING THE ORIGIN AND CON- 

 NECTIONS OF THE ANTERIOR PILLARS OP THE 

 FORNIX. (Schwalbe.) 



A median section has been made through the 

 third ventricle, and the superficial grey matter re- 

 moved at its anterior and lower part as far as a. 

 tli.s, upper part of the thalamus ; th.m, its mesial 

 surface : between the two is the medullary stria, 

 leading from the pineal gland and trigomim habenulse, 

 tr.h, to the anterior pillar of the fornix, c.f; f, 

 bundle of Yicq-d'Azyr ; c.m, corpus mamillare ; 

 i.f, fibres of the inferior peduncle of the thalamus 

 diverging in its substance ; co.a, anterior commis- 

 i, inf undibulum ; r.p, stalk of pineal body ; qu, corpora 



they adhere to the under surface of the corpus callosum, then, curving outwards and 

 downwards over the pulvinar of the optic thalamus, each crus enters the'descending 

 horn of the lateral ventricle, where some of. its fibres are distributed on the surface of 



Fig. 94. VIEW OF THE UPPER SUR- 

 FACE OF THE VELUM INTERPOSITUM, 

 CHOROID PLEXUSES, AND CORPORA 



STRIATA. (From Sappey after Vicq- 

 d'Azyr.) | 



1 , fore part of the tela choroidea 

 or velum interpositum ; 2, 2, choroid 

 plexus ; 3, 3, left vein of Galen partly 

 covered by the right ; 4, anterior 

 pillars of the fornix divided in front 

 of the foramen of Monro ; on either 

 side are seen small veins from the 

 front of the corpus callosum and the 

 septum lucidum ; 5, vein of the 

 corpus striatum ; 6, convoluted 

 marginal vein of the choroid plexus ; 

 7, vein rising from the thalamus opti- 

 cus and corpus striatum ; 8, vein 

 proceeding from the inferior cornu 

 and hippocampus major ; 9, one from 

 the posterior cornu ; 11, fornix 

 divided near its middle and turned 

 backwards ; 12, lyra ; 13, posterior 

 pillar of the fornix ; 14, thesplenium 

 of the corpus callosum. 



the great hippocampus and 

 the remainder are prolonged 

 as the narrow band of white 

 matter known as the tmnia 

 hippocampi or fimbria (fig. 

 89,^). 



On examining the under 



surface of the conjoined posterior parts of the fornix and corpus callosum, the 

 splenium of the latter with its thickened edge and the diverging halves of the 

 fornix appear to enclose between them a triangular structure, marked with trans- 

 verse, longitudinal, and oblique lines. To this part the term lyra has been applied 



