THE CEREBRUM. 



793 



transverse fissure, and insinuates itself between the thalamus opticus and the 

 convolution of the cornu Ammonis. The velum, on arriviiijif beneath the tienia 

 hippocampus, terminates in the choroid plexus — a red, granular-looking cord, 

 which is suspended by its antero-external border, and projects into the interior of 

 the lateral ventricle. 



The rlioi-oid plexuses of the brain {plexus choroidecB) extend from the anterior 

 extremity of the corpus striatum to the bottom of the cul-de-sac, or sphenoidal 

 diverticulum. In the anterior part of the ventricle, they occupy the oblique fissure 

 which traverees that part, to the inner side of the caudate nucleus. In the posterior 

 region, they float in front of tiie cornu Ammonis. Their anterior or internal 

 extremity, more voluminous than the external, always forms a small appendage 



Fig. 436. 



i t 



CA L 

 DIAGRAM OF A TRANSVERSE SECTION OF THE HUMAN BRAIN AT THE MIDDLE PART OP 



THE CORPUS STRIATUM. 



CC, Corpus callosum ; CA, intra-rentricular (or caudate) nucleus of the corpus striatum ; L, extra- 

 ventricular, or lenticular nucleus of the corpus striatum ; ci, CI, internal capsules placed between 

 these two nuclei. 



which remains quite free. They are united to each other, near this extremity, 

 by an intennediate cord, which goes through the foramen of Monro in passing 

 beneath the fornix. 



Like the velum interpositum, the choroid plexuses are formed by a network 

 of arteries and veins. They are often iucnisted in calcareous matter, and may 

 be the seat of more or less voluminous cysts. 



The veins proceeding from this vascular apparatus are very voluminous, and 

 by their union form the great vena Galeni, which bends round the splenium of 

 the corpus callosum to reach the interlobular fissure, and proceeds to the sinus 

 of the falx cerebri. 



The Structure of the Brain. 



The structure of the brain is certainly one of the most interesting points in 



