RECONSTRUCTION OF PAPIO CYNOCEPHALUS 343 



The Vestibular Complex 



The vestibular complex appears on the surface of the reconstruction at 

 about the mid-oHvary level of the brain stem. It is at first a small triangular 

 mass of gray matter located between the lateral surface of the central 

 gray matter and the cephahc extremity of the nucleus of Burdach. 

 As it increases in extent and hulk it acts as a wedge separating the upper 

 extremity of the nucleus of the column of Burdach from the central gray 

 matter. It rapidly increases in its ventrodorsal extent until it becomes a 

 prominent feature in the dorsolateral portion of the tegmentum. Its ventral 

 continuation forms a rather sharp, wedge-shaped mass of gray matter which 

 presents on its lateral surface a distinct concavity in which is lodged the inferior 

 cerebellar peduncle. This portion of the complex is formed by the nucleus of 

 Deiters which reaches its maximum extent at the midventricular level. From 

 this point upward it rapidly diminishes in size, being replaced by the more 

 dorsally situated nucleus of Schwalbe, the triangular nucleus of the vestibular 

 complex. This structure lies dorsal and somewhat mesial to the nucleus of 

 Deiters, mesial to the dorsal cochlear nucleus and crossed by the fibers of 

 the striae acusticae. The triangular nucleus is continued upward for a short 

 distance, gradually attenuating in size and merging with the indifferent 

 reticular matrix of the lateral walls of the fourth ventricle above the level of 

 the lateral ventricular recess. The third element in the vestibular nuclei, 

 the nucleus of Bechterew, is found in the lateral wall of the ventricular for- 

 mation and is not represented in the reconstruction. 



The Cochlear Complex 



The cochlar complex seems to be definitely less developed than that 



in the three preceding forms. The nuclear masses are relatively small and 



poorly developed. The same arrangement is found to be present, that is, 



the almost complete investment of the entering nerve fibers. by the nuclear 



