178 



ANATOMY AND PHYSIOLOGY OP 



the cranium to its base ; whence, greatly diminislied in 

 breadth it continues onward to the os sphcnoidos. 



SINUSES OF THE DURA MATER. 



Q. What are the names of the principal sinuses of 

 the dura mater? — A. The superior or longitudinal 

 sinus; two lateral, cavernous, and sub-occii^ital sinuses, 



riA MATER. 



Q. "What is the situation of the pia mater ? — A. It 

 surrounds and closely invests the convolutions of the 

 brain, and passes into the ventricles, furnishing them 

 ■with an internal membrane. 



Q. AVhat is the structure of the pia mater? — A. It 

 presents a smooth exterior surface ; next the brain it 

 is rough and villous, and is composed of a network of 

 blood-vessels, which are united together by a delicate 

 cellular tissue. Being highly vascular, it is supposed 

 that the blood-vessels of the brain ramify in it before 

 entering the latter. 



ARACUXOID MEMBRAXE. 



Q. "Where is the tunica arachnoidea situated ? — A. 

 It is a delicate and transparent membrane, spread 

 imiformly over the sm'face of the brain. 



CEREBRUM. 



Q. Where is the cerebi*um situated ? — A. It occu- 

 pies the superior part of the cranium. 



Q. AVhat is its form, and how is it dinded ? — A. It 

 is oval, convex above and concave below, and is diA-ided 

 by a longitudinal fissure along its middle, into which 

 the falx cerebri descends. Its di\isions are denom- 

 inated hemispheres. 



Q. What is the appearance of the sm-face of the 

 cerebrum? — A. It is covered with eminences called 

 convolutions. 



Q. Of what is the substance of the brain supposed to 

 consist ? — A. Of two kinds of matter ; the external is 

 called cortical or cineritious, and the internal is termed 

 medullary. 



Q. What is the color of the cortical? — A. Red- 

 dish-ash. 



Q. What is the color of the medullary portion ? — 

 A. Of a milk-white hue. 



CORPUS CALLOSXM. 



Q. What is the situation of the corpus callosum ? — 

 A. It is an oblong Mhite body, located at the bottom of 

 the fissure which divides the two hemispheres of the 

 brain. 



Q. What docs the corpus callosum join on each 

 side? — A. Its edges blend vdth. the medullary sub- 

 stance of the two hemispheres of the cerebrum. 



Q. What name is given to the medullary substance 

 of both hemispheres, together with the corpus callosum, 

 when the usual anatomical section is made? — A. By 

 cutting off" the hemispheres of the cerebrum nearly 

 even with the corpus callosum, there is seen a large 



oval mass of medullary substance, called the centrum 

 ovale. 



LATERAL VENTRICLES. 



Q. What are the lateral ventricles ? — A. Two cavi- 

 ties situated beneath the corpus callosum and medullary 

 arches of the cerebrum. 



Q. What divides the lateral ventricles from each 

 other? — A. The septum lucldum. 



Q. Name the parts which are generally considered as 

 the contents of the lateral ventricles. — A. They are 

 the corpora striata, the hippocampi, plexus choroides, 

 fornix, and the thalami nervorum opticorum. 



Q. What is the situation and form of the corpora 

 striata? — A. They are found on the lower and back 

 parts of the ventricles, projecting into the centre of 

 the canities, where they expand as they approach the 

 septum ; grow narroAver and recede from each other 

 above ; below, they extend to the anterior cornua. 



HIPPOCAMPI. 



Q. What is the situation of the liippocampi ? — A. 

 They occupy the superior spaces of the ventricles in 

 contact with the septum. 



Q. From whence do they originate ? — A. From the 

 centres of the hemispheres. 



Q. What is their structure? — A. They consist of 

 alternate laminae of medullary and cortical matter. 



PLEXUS CHOROIDES. 



Q. What is the situation of the plexus choroides ? — 

 A. They are situated in the channel between the 

 corpus striatum and hippocampus. 



Q. Describe the appearance of the same ? — A. It is 

 a soft vascular substance, consisting of a plexus of 

 minute blood-vessels; it makes its appearance from 

 behind the fornix, and ends abruptly in a round bulbous 

 mass. 



FORNIX. 



Q. Describe the fornix audits situation? — A. The 

 fornix is that pai't wliich receives the posterior border 

 of the septum lucidum. It is extended after the 

 manner of an arch, between the corpora stratia below 

 and the heads of the hi])pocampi above, where it forms 

 a junction Avith the corpus callosum. 



Q. Describe the processes or crura of the fornix ? — 

 A. The two inferior crura spring from the corpus 

 albicantium, at the base of the brain, and finally unite; 

 thus united, they appear within the ventricles and con- 

 stitute the body of the fornix. The superior crura 

 proceed from the upper end of the fornix, and descend 

 into the superior cornua of the lateral ventricles, and 

 end in sharp, pointed extremities. 



TILAXAMLV. 



Q. What is the situation of the thalamia nervorum 

 opticorum ? — A. They form the upper and back parts 

 of the lateral ventricles. 



Q. Describe the thalamia. — A. They have a white 



