280 



THE RHOMBENCEPHALON. 



longitudinal in the formatio reticularis near the ventricular gray 

 matter and medial to the root of the abducent nerve. At that 

 point they bifurcate and one branch runs upward and the other 

 downward. The descending branches of the crossed fibers (lateral 

 ponto-spinal tract) pass through the substantia reticularis grisea 

 of the medulla and the lateral area of the spinal cord throughout 

 its length ; they end in the center of the gray crescent in successive 

 segments until exhausted near the end of the cord (Tschermak, 



Fig. 89. Diagram of a transverse section through the junction of the medulla and 

 pons showing the roots and nuclei of the eighth cranial nerve and the auditory 

 paths in the pons. (After Morris's Anatomy.) 



a. Bechterew's nucleus, b. Nuc. of descending root. c. Restiform 'body. d. Lat. 

 cochlear nucleus, e. Ventral nucleus, f. Vestibular nerve, g. Semicircular canals, h. 

 Cochlear nerve, i. Cochlea, j. Dorso-lateral nucleus (Deitersi). k. Dorse-medial nucleus. 

 1. Lateral fillet, m. Superior olivary nucleus, n. Nucleus of trapezoid body. o. Trapezoid 

 body. 



Barker). The uncrossed fibers from the reticular nuclei enter 

 the medial longitudinal bundle of the same side and there branch 

 T-like. The descending branches (anterior ponto-spinal tract) 

 run with this bundle into the anterior column of the spinal cord, 

 through which some of them continue to the end. They occupy 

 the outer side of the anterior funiculus and end in succession in 

 the anterior columna of gray matter (Tschermak and Barker). 

 Just what is the destination of the ascending branches of either 

 group of fibers has not been determined. J. S. Collier suggests 

 that these tracts from the reticular nuclei should be called the 

 crossed and uncrossed ponto-spinal tracts (Brain, Vol. 24, 1901). 



