OF THE NERVUS OCTAA 7 US. 113 



incision goes through the portio interim , damages partially or 

 totally the nucleus of DEITERS , divides the area ovalis , consequently 

 separates the intermediary bundle from its origin, cleaves often the 

 stratum latero-dorsale and may damage the ventral auditory nucleus , 

 running between its ventro-distal part and its latero-dorsal part. It 

 may damage both roots , or one , or even none at all , this depends 

 on its being made more or less deep. Only the beginner must take 

 care , not to incide too far proxirnally , otherwise the pedunculus 

 cerebelli superior may be lesioned, (which is not a great danger 

 and may be done on purpose) and the end of the incision may be 

 found in the lateral fillet. 



Now in Plate XIX, XX, XXI fig. 25, Plate XVI and XVII 

 fig. 20 and Plate XXI, XXII fig. 28 such dorsal sections are 

 drawn. Plate XIX, XX, XXI fig. 25 represent the drawings of 

 an oblongata wherein this section was made on the two sides. 



In cases that the nucleus ventralis is touched - even if its 

 ventro-distal end is not at all degenerated - - the ventral system 

 degenerates nearly as intensely as after section of its lateral trunk. 



In that case , the degeneration is less intensive in its distal part. 

 Even if the dorsal section be made on both sides a large number of 

 intact fibres is found between the two olivary bodies (Plate XIX 

 fig. 25 E, Plate XX fig. 25 E and G) , probably those, which 

 are not yet medullated at the animal's birth and do not degenerate 

 or atrophy, unless the nucleus olivaris superior be lesioned. 



Subsequent to this section , we meet for the first time with the 

 degeneration a system of transverse fibres , originating in the dorsal 

 system and joining the ventral system at its most proximal end. 



They are the transverse fibres of MONAKOW, which leaving the 

 dorsal system at the level of the nucleus of the VI th nerve, cross 

 the raphe ventrally from the fasciculus longitudinalis posterior in a 

 dorso-ventral oblique direction in order to reach the dorsal top of 

 the contra-lateral oliva. In the medullary surroundings of this 

 nucleus they may leave a part of them. 



But the greater part of those fibres continues in the lateral 

 layer of the olivary body and united with a part of the small transverse 

 fibres from the ventral and intermedial system , they reach the medul- 

 lary surroundings of the ventral nucleus lemnisci and bend upward. 



In frontal sections this nucleus is seen as an acorn in a shell of 

 degenerate queer-sectioned fibres, surrounding it from three sides, 

 at the dorsal, ventral and lateral side (Plate XIX fig. 25 C, D, E). 



The nucleus itself is filled up with degenerate fibres and dis- 

 persed black globules. 



Vertiand. Ron. Akad. v. Wetensch. (Tweede Sectie Dl. XIV). 8 



