CEREBRUM. 



159 



Pituitary Gland, is a vascular mass of a light colour, situated in 

 the sella turcica. It consists of two lobes. 



Longitudinal Fissure, separates the two hemispheres of the cere- 

 brum laterally, and contains the falx cerebri. 



Corpus Callosum, is a white, arched band, seen at the bottom of 

 the longitudinal fissure, forming a commissure between the two 

 hemispheres. It is three inches and a half long, and about an inch 

 broad. Its fibres are for the most part transverse, and consist of 

 medullary matter, with the exception of a ^ew, which pass longitu- 

 dinally, and are called the raphe. 



Septum Lucidiwi, is a vertical partition, consisting of two laminae, 

 and separating the lateral ventricles. Its upper edge is in contact 

 with the corpus callosum, and its lower with the fornix. 



For?iix. — It is a triangular, medullary arch, whose base is con- 

 tinuous W4^ the corpus callosum posteriorly, and whose apex divides 

 into two crura, which terminate in the eminentia ma7nmillares ; 

 its under surface is termed lyra. Under these crura is the fora?nen 

 of Monro, by which the third and two lateral ventricles communicate. 



Velum Interpositum, is a triangular reflection of pia mater, imme- 

 diately under the fornix ; its edges contain a plexus of veins called 

 plexus choroides. 



Pineal Gland, is a small, reddish-gray, conical body, situated upon 

 the tubercula quadrigemina,, and connected by two crura with the 

 optic tubercles. 



Tubercula. Quadrigemind are four prominences situated over the 

 junction of the pons and crura cerebri. Under them is a passage 

 called aqueduct of Sylvius, or iter e tertio ad ventriculum quartum. 



Corpus Striatum, a gray mass of an oblong shape, situated in 

 the lateral ventricle on either side. It is medullary within. 



Thalamus Opticus, is an oval, convex mass, behind the corpus 

 striatum on each side. It consists of a mixture of medullary and 

 gray matter, and has three prominences called corpora geniculata, 

 one on either side, and one in front. It is connected with its fellow 

 by some cineritious substance, called the soft commissure. 



TcBnia Striata, is a thin edge of medullary matter, in the groove 

 between the corpus striatum and thalamus opticus. 



Hippocampus Major, is a scroll extending into the inferior cornu 

 of the lateral ventricle, the extremity of which resembles a foot, and 

 is called the pes hippocampi. 



Corpus Fimhriatum, or Tcenia Hippocatnpi, is a thin edge of 

 medullary matter upon the concave side of the hippocampus major; 

 beneath which is a layer of cineritious matter, having a serrate ap- 

 pearance, and called the fascia dentata. 



Hippocampus Minor, or Ergot, resembles a cock's spur; is a 

 conical elevation pointing backwards into the postjerior cornu. 



Ventricles of the Brain. — These are five in number. They are 

 called the right and left lateral, the third, fourth, dind fifth ventricles. 



