2 1 2 ANA TOMY AND PHYSIOLOG Y FOR NURSES 



The corpus callosum is the transverse portion of the 

 brain connecting the two hemispheres ; it is about 4 inches 

 long. It is composed of a body, a genu, and a splenium. 

 It roofs in the lateral ventricles of the brain. 



There are five ventricles in the brain. The two lateral 

 are covered with the corpus callosum, and are formed by 

 the folding backward of the cerebral lobes. They contain 

 a quantity of a serous fluid, which, when it occurs in ex- 

 cess, as it sometimes does in children, constitutes the dis- 

 ease known as hydrocephalus. It has an anterior, a 

 middle, and a posterior horn. 



The third ventricle lies between the optic thalami and 

 extends to the base of the brain. 



The fourth ventricle is situated between the cerebellum 

 and the posterior parts of the medulla oblongata and pons 

 Varolii. 



If a perpendicular section of the brain were made, the 

 lateral ventricles, as well as the third, would be seen; the 

 corpus callosum, and the fornix and velum interpositum 

 below it, would also come into view. 



The fornix is a layer of white matter, arranged in the 

 form of an arch, beneath the corpus callosum. 



The velum interpositum is a reflection from the pia 

 mater, which penetrates the ventricles through the fissure 

 beneath the posterior border of the corpus callosum. It 

 is a vascular veil, and is rolled up in form of a fringe, which 

 is called the choroid plexus. These plexuses are made up 

 of minute arteries, and communicate with each other 

 through the foramen of Monro. The foramen of Monro 

 is not really a foramen, but simply a communication 

 between the third and the two lateral ventricles. The 

 venae Galeni, two in number, return the blood through 

 these parts and ventricles into the straight sinus. 



The optic thalamus is an elevation upon the floor of the 

 lateral ventricles immediately behind the corpus striatum. 



