RECONSTRUCTION OF H\ LOBATES HOOLOCK 



451 



development becomes more extensive until it completely invests the pyram- 

 idal tract, thus forming the superficial and deep layers of the pontile 

 nucleus. The superficial layer is convex in contour, corresponding to the 



FIG. 214. DORSAL SURFACE OF GRAY MATTER OF BRAIN STEM, 



HYLOBATES HOOLOCK. 



Key to Diagram, inferior collicul., Inferior Colliculus; nucl. of deiters, Nucleus of Deiters; nucl. of 



GOLL, Nucleus of GoII; ret. form.. Reticular Formation; tub. accousticum, Tuberculum Acusticum. 



surface configuration of the pons itself, whereas the deep layer is more or less 

 straight or somewhat concave. Dorsally the ^mesial buttress comes into 

 approximate contact with the ventral surface of the reticular formation. The 

 same arrangement is found in the lateral buttress which, although irregular 

 in outline, comes into intimate relation with the ventrolateral angle of the 

 reticular formation. Between these two points of fusion, however, the ventral 

 surface of the reticular formation and the deep layer of the pontile nuclei are 

 hollowed out by the trapezoid body. 



The scattered collections of gray matter which pass across the tunnel 

 formed within the pontile nuclei are considerably increased. Continuing 



