HEAD. 93 



medulla oblongata, peduncnliim cerebelli or crura cere- 

 belli, valve of Yieussens, corpora quadrigemina and thai- 

 ami optici; lateral faces present the proiile of the 

 medulla oblongata, of the pons Varolii, of the pcdunc- 

 ulum cerebri and cerebelli, of the corpora quadrigemina 

 and thalami optici ; posterior extremity is continuous 

 with the spinal marrow ; anterior extremity passes into 

 the corpora striata. 



1. Medulla OBLONGATA. — Division: Four faces: in- 

 ferior shows the corpora pyramidalia, a transverse band, 

 some arciform fibres, the corpus olivare, the origin of 

 the sixth cranial pair, of glosso pharyngeal and of the 

 pneumogastric ; superior face is covered by the cerebel- 

 lum, forms the floor of the fourth ventricle and shows 

 the calamus scriptorius and the corpora restiforma; 

 lateral face exhibits the profile of the corpora resti- 

 forma and corpora pyramidalia. 



2. Pons Yarolii with its two borders and two ex- 

 tremities, which form the middle crura cerebelli. 



3. Crura cerebri. — Separated from each other by 

 the interpeduncular fissure which bifurcates to circum- 

 scribe forward the mamillary or pisiform tubercle, lim- 

 ited behind by the pons Yarolii, in front by the optic 

 nerves, laterally and above by the corpora quadrigem- 

 ina and thalami optici; it forms laterally the band of 

 Keil or lateral triangular fasciculus. 



