EFFERENT, OR MOTOR PATHS. 373 



red nucleus to the center of the gray crescent in the opposite side 

 of the spinal cord. Crossing the median raphe at once, in the 

 hypothalamic region through the ventral tegmental decussation, 

 (Foreli), the impulses descend by way of the rubro-spinal tract, 

 through the ventral part of the formatio reticularis of the mid- 

 brain and pons, in the medial part of the lateral fillet, then through 

 the lateral area of the medulla, among the fibers of the anterior 

 ascending cerebello-spinal tract, and finally down the spinal cord, 

 through the ventral portion of the lateral pyramidal area, to their 

 destination in the gray matter. From the center of the gray cres- 

 cent they proceed with or without transferring to the roots of the 

 spinal nerves, and are conducted to the v muscles. 



(2) Indirect Route. Impulses from the red nucleus may also 

 run through the brachium conjunctivum, chiefly the opposite 

 one, to the nucleus dentatus; and thence, by axones from that 

 nucleus, down the anterior descending cerebello-spinal tract, 

 which continues their path to the columna anterior of the cord. 



PONTO-SPINAL PATHS. The ponto-spinal tract is the 

 name suggested by Collier for the tracts originating in the nuclei 

 of the reticular formation, chiefly in the pons, and descending 

 to the gray matter of the spinal cord. There are two of them on 

 either side. The medial ponto-spinal tract accompanies the 

 medial longitudinal bundle down the anterior ground bundle of 

 the cord without decussating, unless the crossing occurs near the 

 termination. The lateral ponto-spinal tract, which is crossed, 

 decussates in the brain stem near its origins and descends in the 

 lateral column of the spinal cord. Just how the impulses reach 

 the nuclei centrales and nuclei laterales of the formatio reticularis, 

 in w r hich the ponto-spinal tracts take their origins, cannot be 

 definitely stated; but, having arrived in them, they descend to 

 both crescents of the spinal cord and apparently enter into all 

 its segments. The anterior nerve roots complete the paths. 



Short Fiber Paths'. Those are paths in the formatio reticula- 

 ris chiefly, (i) Impulses having reached the great ganglia of 

 the cerebrum and mid-brain may run through many relays down 

 the formatio reticularis of mid-brain, pons and medulla and the 

 antero-lateral fasciculus proprius of the spinal cord, to the gray 



