SURFACE AND INTERIOR OF CEREBRUM. 87 



transverse and marked along the central line by a raphe ; 

 if the convolution called g3 r rus fornicatns be cut through 

 transversely, and turned one part forward and the other 

 backward, a white, longitudinal band of fibres, lying upon 

 the corpus callosura, will be exposed, called the stride lon- 

 gitudinales laterales, or covered band of Reil. In front, 

 the corpus callosura bends round to the base of the brain, 

 the bend being called its genu ; posteriorly it forms a thick 

 rounded border ; on each side it forms the roof of the 

 cavities in the hemispheres called the lateral ventricles, 

 and, by its under surface, is connected with the septum 

 lucidum anteriorly and with the fornix posteriorly. 



The ventricles of the brain are cavities which exist in its 

 interior ; they are five in number. One is found in the cen- 

 tral part of each hemisphere; these are called lateral ven- 

 tricles, and constitute the first and second ; the third 

 occupies the middle line of the brain near its under surface; 

 the fourth is between the cerebellum and the posterior 

 surface of the medulla oblongata and pons Yarolii; the 

 fifth is in the partition which separates the two lateral 

 ventricles from each other. 



The lateral ventricle of either side is displayed by shaving off as 

 much of the corpus callosum and central medullary substance of each 

 hemisphere as constitutes its roof; the escape of a fluid which is 

 ordinarily present, warns the dissector of his arrival in the cavity of 

 the ventricle. 



The LATERAL VENTRICLE is a narrow interval extending 

 into the anterior, middle, and posterior lobes of the hemis- 

 phere by three prolongations called cornua; the anterior 

 cornu is directed outward ; the posterior, which is small, 

 turns inward, and the descending, middle, or inferior cornu 

 penetrates in a spiral manner into the middle lobe. This 

 ventricle presents from before backward the following parts 

 for examination, viz : 



Corpus striatum, Hippocampus major, 



Taenia semicircularis, Hippocampus minor, 



Optic thalamus, Septum lucidum, 



Choroid plexus, Fornix. 



The corpus striatum, a large oval body in the anterior 

 part of the lateral ventricle, is so called from the striated 

 lines of white and gray matter which are seen upon cutting 

 into its substance. The broad end, directed forward, is 



