OP THE NERVUS OCTAVUS. 81 



collaterals now detach themselves and penetrate into the tuberculum. 

 In frontal sections they appear situated as the spakes in a wheel. 

 They are radial fibres to this ganglion which, sectioned frontally, 

 has the shape of a circle segment. Those radial fibres are only 

 traceable unto the level , where the great pyramide-shaped cells 

 of the ganglion are found. 



Now on horizontal sections again the fibres of the stratum medul- 

 lare profundum are touched in a longitudinal direction and again 

 the collaterals leave them perpendiculary. 



In this way their situation is the cause of a very peculiar aspect 

 of the degenerated ganglion, if coloured by Marchi-method. 



It appears to be divided into two rings, the outer is quite free 

 from degenerated fibres and extends to the layer of large cells. 

 The inner ring is thickly specked with very small black granules - 

 the degenerated collaterals and radial fibres, also containing 



these black granules, are easily to be distinguished. The two rings 

 are resting upon the deep medullary layer (fig. la Plate I, Plate 

 VIII fig. 15 N. G, Plate XI fig. 16 L and M, Plate XIV fig. 

 14 C) and bordering the outer (non degenerated) as well as the inner 

 (degenerated) ring the large pyramidal cells appear. In this way 

 Murchi-degeneration divides the tuberculum acusticum into four or 



O 



five layeis (Plate VI fig. G). Named from its centrum towards the 

 periphery they are : 



l e . The deep medulla or the stratum medullare profundum 

 containing root-fibres chiefly of the dorsal root. 



2 e . The deep grey matter or the stratum griseum profundum 

 containing degenerated collaterals of root fibres and small cells. 



3. The middle grey matter or the stratum griseum medium- 

 containing the large nerve cells. 



4 e . and 5. The superficial grey matter and fibres or the stratum 

 griseum superficial and the stratum medullare superficiale , where 

 no degeneration is found after rootsection. 



Moreover, in the same way as the nucleus ventralis, the tuber- 

 culum acusticum is receiving the greater part of the root-fibres at 

 the distal end. At its dorsal and proximal end the black globules 

 in the inner ring are less thickly spread and normal fibres mix 

 between the degenerated of the stratum profundum medullare, 

 seeking their way to the middle layer of the radiation found dor- 

 sally of the area ovalis. 



Now , when following this radiation in proximal direction , the 

 aspect changes, because the tuberculum acusticum gradually takes 

 a more lateral instead of a dorsal situation. At the same place the 



Verhand. der Kon. Akad. v. Wetensch. (Tweede Sectie.) Dl. XIV. $ 



