oe) 
NO 
DISSECTION OF THE BRAIN. 
Remove carcfully with forceps and knife the corpus 
callosum until the lateral ventricles are exposed, taking 
care not to imjure the fornix, which les tmmediately 
beneath. 
c. Tue LATERAL VENTRICLES, one on each side, 
fully exposed after complete removal of the corpus 
callosum. In each three chambers or horns may be 
distinguished; the azderzor cornu, a narrow slit run- 
ning forward and separated from the anterior cornu 
of the other side by a vertical partition—the septum 
lucedum ,; the descending cornu, situated posteriorly 
and curving downward and outward; the fosterzor 
cornu, situated at the most posterior end of the ven- 
tricle, a small diverticulum running backward, very 
inconspicuous in the dog. 
d. THe Septum Lucrpvum is the vertical partition 
lying between the anterior cornua of the two ventricles. 
It contains within its walls a small cavity, the so- 
called 5th ventricle, not formed by the closing in of 
the embryonic medullary tube like the other true 
ventricles of the brain. 
e. THE Corpus STRIATUM is the oval mass pro- 
jecting into each anterior cornu from the side of the 
cerebral. hemisphere, Only apart of “the iconpours 
striatum is seen in the dissection; the remainder is 
concealed in the» walls (of the hemisphere!” ites 
originally an outgrowth from the floor of the vesicle 
of the cerebral hemispheres, and contains two nuclei of 
eray matter in its interior—the zacleus caudatus, con- 
tained within the part which projects into the ven- 
tricle, and the zzucleus lentrcularzs, contained within 
the part buried in the wall of the hemisphere. 
Lay open the descending cornu on one side by care- 
fully cutting away the sides of the cerebral hemisphere. 
