RECONSTRUCTION OF PAPIO CYNOCEPHALUS 



337 



accessory olive makes its appearance at about the upper level of the 

 pyramidal condensation as a Hat band of gray matter disposed transversely 

 with a slight inclination dorsally at its mesial extremity. The mesial extrem- 



FIG. 157. DORSAL SURFACE OF THE GRAY MATTER OF THE BRAIN STEM, 



PAPIO CYNOCEPHALUS. 

 Key to Diagram, dors, cochl., Dorsal Cochlear; inf. coll., Inferior CoIIiculiis; nucl. of burdach, Nucleus 

 of Burdach; n. of d., nucl. of deiters and nucleus of dtrs.. Nucleus of Deiters; nucl. of goll, Nucleus of 

 Go!!; RET. FORM., Reticular Formation; sub. gel. rol. and subst. gel. rolando. Substantia Gelatinosa of 

 Rolando; vent, coch., Ventral Cochlear Nucleus. 



ity of the nucleus turns backward upon itself, forming a hook-shaped mass of 

 gray matter. 



The dorsal accessory olive appears only sHghtiy above the level of the 

 appearance of the ventral accessory nucleus as a small lamina of gray matter 

 which continues upward as a rather narrow strand. At the level of appearance 

 of the main mass of the inferior olivary nucleus it expands into a narrow 

 flattened sheet which lies dorsal to the hilus of the inferior olivary nucleus. 

 The main nucleus appears as the fourth ventricle begins to open in the form 

 of a loop-shaped layer of gray matter, presenting a few simple reduplica- 



