i6o 



THE NERVOUS SYSTEM 



arise in the dentate nucleus of the cerebellum; they cross the median plane 

 in the tegmentum at the level of the inferior colliculi and end either in the red 

 nucleus or in the thalamus. 



According to Cajal (1911) the fibers of the brachium conjunctivum give off two sets of 

 descending branches, which he has seen in Golgi preparations of the mouse, rabbit, and cat. 

 The first group are collaterals given off as the brachium enters the dorsal part of the pons 

 and before its decussation (Fig. 115). They descend into the pons and medulla oblongata 

 and constitute a direct descending tract from the dentate nucleus of the cerebellum to the 

 reticular formation of the pons and medulla oblongata. The second group of descending 



Rubrospinal tract x 

 Rubroreticular tract v 



From frontal lobe and corpus strialum 

 Thalamus 



Red nucleus 

 Brachium conjunctivum 

 Dentate nucleus 



\ 



Pons 

 Rubrospinal tract 



Medulla oblongata 



Reticulospinal tract 



Spinal cord 



Fig. 115. Diagram showing the connections of the red nucleus: A, Ventral tegmental 

 decussation; B, decussation of the brachium conjunctivum; Cand D, descending fibers from bra- 

 chium conjunctivum, before and after its decussation respectively. 



branches is formed by the bifurcation of the fibers of the brachium conjunctivum just beyond 

 the decussation, and constitute a crossed descending tract from the dentate nucleus, which 

 can be followed by degeneration methods through the reticular formation of the brain stem 

 and probably into the anterior and lateral funiculi of the spinal cord (Fig. 115). 



The red nucleus (nucleus ruber) is a very large oval mass of gray matter, 

 which in the fresh brain has a pink color. It is located on the path of the brach- 

 ium conjunctivum in the rostral part of the tegmentum (Fig. 116). In trans- 

 verse sections it presents a circular outline and can be followed from the level 

 of the inferior border of the superior colliculus into the hypothalamus. In its 

 caudal portion it contains great numbers of fibers derived from the brachium 



