6i6 



THE NERVOUS SYSTEM 



ventral surface; others cross to the opposite side of the pons and then become 

 longitudinal, passing on to the tegmentum. 



2. Fibers longitudinal in direction are arranged in larger or smaller bun- 

 dles and are separated by gray matter. Most of these fibers are pyramidal 

 fibers which pass down to the pyramids of the medulla. 



3. The dorsal portion of the pons is made up to a considerable extent of 

 the reticular formation of the tegmental region together with one or two 

 distinct bundles of longitudinal fibers. The chief longitudinal bundle, 

 situated at the junction of the ventral two- thirds with the dorsal third, is the 



FIG. 383. Scheme to show the connections of the Posterior Longitudinal Bundle. 

 (Cunningham, modified from Held.) 



fillet, including a, the larger mesial fillet, a sensory tract previously described 

 arising in the gracile and cuneate nuclei, and b, the lateral fillet, an auditory 

 tract, see figure 414. The second, the posterior longitudinal bundle, is situated 

 on each side of the mid-line, just internal to the mesial fillet. Some of the 

 connections of the posterior longitudinal bundle are shown in figure 383. 



4. In the upper part of the pons there is a mass of gray matter containing 

 pigment, the locus ceruleus; and in the back part a second mass of gray matter, 

 the superior olive, which is connected with the auditory conduction path, 

 figure 414. 



