OF THE NERVUS OCTAVUS. 85 



system there. Between them many fibres still penetrate into the 

 portio interim towards the region where the radix descendens of 

 the n. VIII is found. They are less in number than at the other side. 



Though the ventral root has completely lost its fibres, the des- 

 cendent root - - though its atrophy may be called very important - 

 still contains many fibres. Therefore secundary fibres existing in 

 this area may be presumed. 



The atrophy method therefore makes from the stria acustica the 

 exact reverse of what Marchi-method makes from it. The latter shows 

 degenerated fibres on both sides of a normal secundary layer, the 

 former shows the central layer without the rootfibres bordering it. 



In the same way as the partial atrophy was formerly demonstrated 

 in the corpus trapezoides , it is now found in the stria acustica. 

 Indeed , between the stria acustica and the corpus trapezoides in 

 many regards a paralel may be drawn. 



Both are atrophying partially , both are possessing an important 

 secundary system bordered on the two sides by root-fibres, both 

 obtain secundary fibres from the same ganglia ventral nucleus and 

 tuberculum acusticum. 



Frontal sections through the medulla of young born animals or 

 of elder foetus , also show very clearly the existence of the different 

 layers in the stratum latero-dorsale and in the stria acustica. 



In the new-born cat (Plate I fig. 5 in /3) for instance, two layers 

 of medullated fibres , an internal and an external one are separated 

 by a layer of non medullated fibres. 



In the elder foetus of a rabbit (Plate XII fig. 17 A in ft] the 

 medullated internal layer forming the intermedia] system , and the 

 medullated external layer forming the stratum medullare profundum 

 of the tuberculum are separated by a portion without medullated 

 fibres. 



If compared with the stratum latero-dorsale , as Marchi-inethod 

 after cochlea-removal or root-sections shows it (fig. ^a on Plate I 

 in /3), the similitude is very striking. 



The paralellism between the dorsal and the ventral systema again 

 appears very clearly. 



Both possess an external border of root-fibres , a secundary system 

 and on their internal border the rootfibres of the intermedial system. 



The atrophy in the primary nuclei , which accurs months after 

 the rootsection in the young animal, is now chiefiy characterised 

 by an enormous loss of fibres, rootfibres as well as collaterals, but 

 it is remarkable that the loss or the changes in the nervous cells 

 of these nuclei is less evident. Firstly it may be called in mind, 



