DISSECTION OF THE HEAD AND NECK 343 



(cb) Chorioid plexus (plexus chorioideus ventriculi lateralis). The 

 fimbria hippocampi and fascia dentata hippocampi have 

 already been examined. The edge of the fimbria after 

 tearing away the .chorioid plexus is called the taenia fim- 

 briae. 



The student should next remove the remains of the right 

 temporal and occipital lobes ; cut through (a) the fimbria hippo- 

 campi, where it passes into the crus fornicis, and (b) the occipi- 

 tal part of the radiation of the corpus callosum (0. T. forceps 

 major). Next make an incision from the anterior end of the 

 cornu inferius forward, above the level of the uncus, through the 

 polus temporalis. Now separate the lobus temporalis, with the 

 gyrus hippocampi medial to it, from the rest of the hemisphere, 

 the separation taking place along the line of the inferior part of 

 the fissura transversa cerebri. Cut away enough of the lateral 

 edge of the remaining medial part of the corpus callosum to 

 permit of a good view of the septum pellucidum and the f ornix, 

 lying beneath it. Having noted their relations, cut across the 

 remains of corpus callosum behind the genu, gently raise the 

 truncus corporis callosi, and dissect backward, freeing it from 

 the septum pellucidum and, further back, from the fornix. 



Septum pellucidum. 



(a) Layer of septum pellucidum (lamina septi pellucidi). 



(b) Cavity of septum pellucidum (cavum septi pellucidi) (0. T. fifth 



ventricle). 

 Fornix. 



(a) Body of fornix (corpus fornicis). 



(aa) Taenia of fornix (taenia fornicis). 



(b) Crus of fornix (crus fornicis) (0. T. posterior pillar of fornix). 



(c) Column of fornix (columna fornicis) (0. T. anterior pillar of 



fornix). 



(ca) Free part (pars libera columnae fornicis). 



(cb) Covered part (pars tecta columnae fornicis). 



Next cut transversely through the corpus fornicis at its 

 middle and gently reflect the two ends forward and backward 

 respectively. Running medialward from the crus fornicis, infe- 

 rior to the corpus callosum, towards the crus fornicis of the 

 opposite side, observe the commissure of the hippocampus 

 (commissura hippocampi) (0. T. lyra or lyre of David). The 

 space between the commissura hippocampi and the inferior sur- 

 face of the corpus callosum has been called " Verga's ventricle. " 

 One-half of the so-called chorioid tela of the third ventricle (tela 

 chorioidea ventriculi tertii) (0. T. velum interpositum) is now 



