OF THE NERVUS OCTAVUS. 107 



a. The secondary system participating in the systema ventrale nervi 

 octavi and in the systema intermedium nervi octavi. 



In order to study the secundary systems entering in the ventral 

 and intermedial system, it may be presumed, that they originate 

 in the nucleus ventralis N. octavi, in the tuberculum acusticum in 

 the nucleus of DEITEKS and in the oliva superior with its adjoining 

 nuclei. 



I therefore have made two operations, described in the former 

 chapter. 



The first is the section of the corpus trapezoides or of the systema 

 ventrale, laterally from the issue of the facial nerve. 



The second is the ablation of the tuberculum acnsticum and the 

 nucleus ventralis. 



As I have already described, each localised lesion in the central 

 system is followed by a surrounding area, where the nervous 

 elements are lost, not by means of simple degeneration, but (even 

 with the severest asepsis) by means of irritation. Therefore each 

 wound, is surrounded by a more or less extensive area, not stained 

 black with Marchi-method , but characterised as a spot of white 

 colour, wherein here and there black globules are found. 



The section of the lateral trunk of the s} sterna ventrale is made 

 at the entrance of the two roots, with a very thin knife, following 

 the n. octavus through the meatus acusticus, and after some experience 

 this may be done without lesion of the facial root, distally from 

 the entrance of the nervus trigeminus, laterally from its spinal root. 



Such a section is drawn in fig. 22 on Plate XVIII. The lesion 

 itself is represented in x (Plate XVIII fig. 22 A, 13, C, D). The 

 incision enters (fig. 22 C) the medulla ventro-laterally and goes dorso- 

 medially. After cleaving the trunk of the corpus trapezoides, it 

 divides the oval area transversally, causing in this way a degene- 

 ration towards the cerebellum, that needs not be followed here. The 

 surrounding area extends into the dorso-lateral part of the fibres 

 (not into the formatio gelatinosa) of the V th root, and causes a 

 descending degeneration of the dorso-lateral fibres of this root, the 

 ventro-medial fibres being normal (Plate XVIII (fig. 22 D H). 

 The surrounding area also extends into the latero-distal part of the 

 portio interna, dividing the intermediary trunk, which is totally 

 degenerated. 



The incision has also divided the two entering roots. And con- 

 sequently to this rootsection there exists a degeneration in the 



