RECONSTRUCTION OF CALLITHRIX JACCHUS 185 



The main olivary nucleus appears as a small mass of nuclear material between 

 the actual extremities of the accessory olives with which it fuses. It presents 

 no plications. 



FIG. 91. VENTRAL SURFACE OF THE GRAY MATTER OF THE BRAIN STEM, 



CALLITHRIX JACCHUS. 

 Key to Diagram, inf. olive. Inferior Olive; lat. gen. body. Lateral Geniculate Body; pontile. Pontile 

 Nuclei; ret. form.. Reticular Formation; subst. nigra, Substantia Nigra; vent, cochl., Ventral Cochlear 

 Nucleus; v. G. C. and vent. cr. col., Ventral Gray Column. 



The Reticular Formation 



Reconstruction of the reticular formation reveals in general the same 

 characteristics found in the lemur. It provides a matrix through which 

 numerous fasciculi make their way. It is surrounded, except dorsally, by 

 fiber masses passing upward or downward through the stem. Dorsally it 

 comes into contact and merges with the subependymal gray matter which 

 appears as the continuation of the central gray column. The reticular forma- 

 tion originates as small masses of nuclear material appearing between the 

 decussating bundles of the pyramidal tract, which, as these fibers are 



