ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. 



635 



pyramids of the medulla; farther down it is still in connection with 

 the pyramidal tract of the opposite side of the spinal cord. 



2. The middle column., or fillet. 



3. The third group, the posterior longitudinal column, passes 

 along the floor of the fourth ventricle, from which it is separated 

 by a plane of transverse fibers. It is continuous with the anterior 

 column of the cord in order to form the longitudinal commissural 

 column. Some of the fibers of this bundle decussate with their fel- 



.^Ant.copp. quad. 



Optic tract. 



Sup.oliVe. 



Sup. olive. 

 Post, longitudinal bundle. 



Fig. 246. Diagram to Illustrate Some of the Connections of the Nuclei 

 of the Nerves to the Ocular Muscles. (STARLING., after HELD.) 



lows of the opposite side to unite among themselves the nuclei of 

 the motor nerves of the eye and the gray mass of the aqueduct of 

 Sylvius. 



Each bundle is separated from its fellow by a plane of trans- 

 verse fibers : the strata zonale and prof undum. 



The gray substance of the pons is .found isolated in small islands 

 (nuclei of the pons), which are located between the various white 

 layers which have just been mentioned. 



One of these nuclei, the most voluminous of all, is situated near 

 the median raphe at the site of the junction of the inferior and 

 middle thirds of the pons. It bears the name of reticulated nucleus 



