TROGLODYTES GORILLA 



655 



the restiform body. At the upper extremity of this body is another elevation 



upon the hiteral surface, the tubercuKim aeusticum. 



The dorsal surface of the oblongata presents the characteristic infra- 



FIG. 2()6. DORSAL SURFACE OF BRAIN STEM, GORILLA. 



[Actu.il Length 42 mm.| 



Key to Diagram, d. m. St., Dorsomcciian Septum; fovea inf.. Fovea Inferior; ink. coll.. Inferior Collicu- 

 lus; SUP. CEREBL. PED., Superior Cerebellar Peduncle; sup. collicul., Superior Colliculus; tub. trig., 

 Tubcrculum Trigemini. 



ventricuhir and \entricuhir regions. In the infraventricular region, the 

 dorsomedian septum in tlie niidhne separates the two alar plates, each of 

 which is further subdivided by the presence of a dorsal paramedian sulcus. 

 These sulci demarcate the chiva which represents the column and nucleus of 

 GoII and the cuneus representing the nucleus and column of Burdach. 



In this portion of the oblongata the striking features are the prominence 

 of the pyramid, indicating a probable increase in the volitional control over 



