MEDULLA OBLONGATA AND TEGMENTUM OF THE PONS. 397 



position and somewhat ventral to the posterior longitudinal bundle. In 

 man one finds in the same place as in rabbits a large number of transversely- 

 ■divided fibers (Fig. 301, a). But the demonstration by the degeneration- 

 method is wanting to show their connection with the trigeminus. Compare, 

 also, the area in Fig. 199, marked "aus Thalamus." In the midbrain one 

 finds the central trigeminal path lateral to the descending fibers of the pos- 

 terior commissure, and they may be finally traced, according to Wallenberg, 

 into the ventral nucleus of the thalamus, where it approaches the upper 

 fillet, or its end-station. 



S. Ramon y Cajal discovered the same path independently of Wallen- 

 berg, at least in its place of origin, and has given us an exhaustive descrip- 

 tion of the structure of its bulbar nucleus. This contains a multitude of 

 •conspicuous multipolar cells. Around these peripherally arborize the fibers 

 of the trigeminal root, and from these cells arise the axis-cylinders of the' 

 •central tract. Of these the majority pass over to the other side, as stated 

 above, and there extend upward as the most dorsal bundle of the substantia 

 reticularis, a smaller number, however, according to E. y Cajal, remaining 

 •on the same side. There is here a contradiction to the results furnished by 

 the degeneration-method of experiment. 



From the central trigeminal path issue numerous collaterals to the facial 

 nucleus, furnishing the sensory-motor reflex-arc for the face. Section of 

 the trigeminus is, therefore, accompanied by not inconsiderable motor dis- 

 turbances in the face, due to the loss of the sensory control. 



The mkin branch of the fifth, where it enters the pons near the motor 

 nucleus, is called the portio major. In this portio major trigemini are in- 

 •cluded also the fibers of the direct sensory tract descending from the cere- 

 bellum. 



From the exit of the fifth up to the exit of the trochlearis the pontile 

 tegmentum presents a relatively more simple structure than that we have 

 learned lower down. In the last section demonstrated the corpus resti- 

 forme began to separate from the great mass of the cerebellum. It leaves it 

 •entirely now and approaches on either side laterally to the tegmentum, thus 

 forming its outermost boimdary in the dorsal area. 



The lateral boundary further ventral, just over the pontile fibers, is 

 formed by the lemniscus, and more especially by that part of it coming 

 •from the cell-bodies of the sensory nerves, is distinguished as the lateral or 

 inferior lemniscus, as differentiated from the median portion, which comes 

 mostly from the nuclei of the posterior columns of the cord. The frontal 

 portion of the tegmentum is imbedded in the lemniscus fibers, as in a trough 

 <Fig. 253). The horizontal part of this trough belongs mainly to the median 

 lemniscus. It separates in wide extent the tegmental fibers from the al- 

 .ready numerous fibers of the crura in the region of the pons. And so arises 



