THE BRAIN. 125 



What are the parts above-named? Some, as the corpus striatum, optic 

 thalamus, etc., have been described already; the others are 



Corpus Callosum, the great transverse commissure, arching backwards to 

 become continuous with the fornix, reflected below, forming the Peduncles 

 at the entrance of the fissure of Sylvius; and marked above by a depres- 

 sion, the Raphe, and longitudinal elevations, the Strife Longitudinales or 

 Nerves of Lancisi. 



Tcenia Semicircularis, consists of commissural fibres between the corpus 

 striatum and the optic thalamus. 



Choroid Plexus of Veins, is the margin of a fold of pia mater which enters at 

 the transverse fissure, passes up the descending cornu, passes through the 

 foramen of Monroe, and as the Velum Interpositum spreads out over the 

 roof of the 3d ventricle. 



Corpus Fimbriatum, or Tcenia Hippocampi, is a white band, the edge of the 

 posterior pillar of the fornix. 



Fornix, is a commissure situated beneath the corpus callosum, but continuous 

 with it posteriorly, the Septum Lucidum separating them in front. It is of 

 triangular form with the apex in front. Its Anterior Crura curve down- 

 wards to the base of the brain, are there reflected, forming the Corpora 

 Albicantia, and end in the optic thalami. Its Posterior Crura pass down 

 the descending horns of the lateral ventricles, as the Hippocampi Majores. 

 The Lyra is a series of markings on its under surface. 



Septum Lucidum, consists of 2 layers of white and gray matter, lined by 

 epithelium ; is placed vertically between the lateral ventricles, from the 

 raph6 of the corpus callosum above to the fornix below. The cavity in 

 its centre is the 5th ventricle. 



Describe the Cornua of the Lateral Ventricles. The Anterior Cornu 

 curves over the anterior end of the corpus striatum into the anterior lobe. 

 The Posterior Cornu curves downwards and inwards in the occipital lobe, 

 and contains a smooth eminence, the Hippocampus Minor. The Middle Cornu 

 descends into the middle lobe to the transverse fissure at the base of the brain, 

 curving backwards, outwards, downwards, forwards, and inwards (B. O. D. 

 F. I.). On its floor are the following : 



Hippocampus Major, the doubled-in surface of the gyms fornicatus. 



Pes Hippocampi, rounded eminences at the end of the hippocampus. 



Pes Accessorius, or Eminentia Collateralis, between the hippocampi, at the 

 junction of the middle and posterior cornua. 



Corpus Fimbriatum, a continuation of the posterior pillar of the fornix. 



Choroid Plexus of Veins, a process of pia mater, already described. 



Fascia Dentata, the gray serrated edge of the middle lobe. 



Transverse Fissure, at the extremity of the cornu, extending to the median 

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