300 



THE INTERMEDIATE PRIMATES 



structures arc concerned. In other words, the cortico-spinal connection 

 tor the transmission of vokintarv impulses shows expansion in the baboon 

 as compared to the lower forms. The relative increase in the size of the 





FIG. 142. \t,\lKAL SURFACE OF BRAIN STEM, PAPIO C^■^OCEPHALUS. 



[Actual Length 46 mm.] 



Key to Diagram, cer. i'ed., Cerebral Peduncle; pvr. dec, Pyramidal Decussation; trap, body, Trane- 



zoid Body. 



inferior oIi\e points to an expansion m the rellex control ol simultaneous move- 

 ments of eyes, head and hands as well as in all skilled, learned performances. 

 The Pons Varolii. On the ventral surface of the oblongata, at its 

 cephahc extremity, there appears the usual expansion of the neuraxis, the 

 pons Varolii. A sharp line of demarcation separates the oblongata from the 

 pons, the bulbopontile sulcus. A small blind recess at the point where the 

 ventromedian sulcus meets the bulbopontile sulcus, forms the foramen 

 caecum posticum. From the sulcus between the inferior olive and the pyra- 

 mid, libers of the twelfth nerve emerge from the oblongata. At the cephalic 

 extremity of the pons is the t)ptico-peduncular space bounded in Iront by 



