ix.] THE NERVOUS SYSTEM. 373 



cornua. The anterior cornu passes into the frontal lobe. 

 The posterior cornu passes into the hinder or occipital lobe. 

 The third, or descending cornu, passes into the temporal lobe. 

 Certain sulci on the surface of the cerebrum extend so deeply 

 as to produce eminences on the inner surface of the lateral 



FIG. 328. HORIZONTAL SECTION OF PART OF THE BRAIN, the cerebrum and 

 velum interpositum being removed, the fornix and septum iucidum being cut 

 through, and the third and fifth ventricles and the upper surface of the cere- 

 bellum being exposed. 



ac, anterior commissure ; cc, corpus callosum ; cb, cerebellum ; r/, crura of fornix : 

 n, nates ; op, optic thalamus ; pc, posterior commissure ; //, pineal gland ; 

 j, middle, or soft commissure ; st, corpus striatum ; sv, superior vermis ; 

 t, testes ; 4, fourth nerve ; 5, fifth ventricle- on each side of it is a lamina of 

 the septum Iucidum cut through. 



ventricles. One such insignificant structure in the posterior 

 cornu is spoken of as the hippocampus minor j another in the 

 descending cornu has been termed the hippocampus major. 



Careful inspection shows that the septum Iucidum is really 

 double, enclosing a very narrow space the fifth ventricle 

 the laminae of the septum Iucidum passing downwards from 

 ihe corpus callosum to the fornix. 



This fornix is made up of two white cords closely approxi- 

 mated anteriorly and diverging widely behind. Each springs 

 from one of the corpora mammillaria, and the two cords 

 (crura) ascend (side by side) behind the anterior commissure, 

 and with a branch of the foramen of Monro on the outer side 

 of each. They then curve backwards, diverging, but at the 

 same time united by a delicate membrane called the lyra. 

 They become connected with the corpus callosum, and then 

 pass into each descending cornu of the lateral ventricles. 



