120 C. WittKLEit. THE CENTRAL COUilSE 



the IV th nerve appears, they surround this nucleus from its lateral 

 side, lying now nearly dorsal from this fasc. long. post. (Plate XIX 

 fig. 25 A). 



Now on the right side, degenerate fibres taking the same way 

 are also found, though in a smaller quantity, and they also may 

 be followed through the proximal part of the stria medullaris, 

 between the normal cells, which are left by the partial destruction 

 of the right DEITERS nucleus. 



Tliis ascending tract in the dorsal system degenerating here on 

 both sides, may be called the tractus DEITERS ascendens. Degene- 

 rating partially after rootsection , it does so totally within six days 

 after the section of the dorsal systema, as DEITERS nucleus is 

 incised. The tract gives an important number of fibres between 

 the cells of the IV th nucleus, also to the distal end of the third 

 nucleus and not only this, but within six days I found a very 

 intense degeneration of the roots of the N. trochlearis. 



On horizontal sections (Plate XVI fig. 20 D) the degenerated 

 tract is also found after the division of the dorsal system. It is 

 found degenerated on the operated side and forms a powerful 

 bundle of fibres from the nucleus of DEITERS towards the same- 

 sided motor nuclei of the eye. 



However the tractus ascendens of DEITERS is only one of the many 

 systems of fibres degenerating after the destruction of that nucleus. 



In following (Plate XX fig. 25 E L) the damaged nuclei 

 DEITERS to their distal ends, there appears a new bundle of dege- 

 nerate fibres. Apparently it accompanies for a short moment the 

 descending root of the N. octavus, lying at its medial side (Plate XX 

 fig. 25 E tr. DEIT. asc. -j- r. desc. N. VIII) but soon it leaves 

 the root and radiates in a medio-ventral direction crossing the facial 

 issuing root (fig. 25 E and G). 



In horizontal sections this radiation is found as a field of dege- 

 nerated queer-sectioned fibres medially from the facial root and 

 surrounding it (fig. 20 E fasc. DEIT. desc.). 



As the root is crossed it slightly bends distally until the root- 

 fibres leaving the VII th nucleus are reached (fig. 25 H). There 

 the bundle forming an angle of nearly 90, abruptly takes a lon- 

 gitudinal and distal course (Plate XX fig. 25 I L). 



It is the tractus DEITERS descendens. Horizontal sections (Plate 

 XVII fig. 20 E and E. tr. DEIT. desc.) are very useful to demon- 

 strate this part of this tract and it may likewise be plainly demon- 

 strated in the double-sided section of the dorsal systema, even 

 better on the right, because the incision falling not very proxi- 



