166 C. WINKLER. THE CENTRAL COURSE 



not yet myelin at that time (the stratum c of the corpus trape- 

 zoides, a large part of MONAKOW'S fibres). 



The ventral spino-cerebellar ascending tract only for a short time 

 is a constituent of the lateral fillet, as it soon takes its distal way 

 to the nuclei tecti, and the descending hook-like bundle, descending 

 from the nuclei tecti towards the corpus restiforme, also soon leaves it. 



But the remainder of its fibres are going proximally, towards 

 the nucleus corporis quadragemini posterioris, to the corpus geni- 

 culatum mediale and. to the sub-thalamic region. 



Whatever now may be the function, probable a very complica- 

 ted sensu-motor function of the corpus quadrigeminum posterius 

 is unknown. So much is sure, that its ablation never causes the 

 forced attitude of eyes, head and neck, characterising the rootsec- 

 tion of the octavus, the ablation of the tuberculum acusticum, the 

 lesion of the DEiTERS-nucleus, shortly all operations in the region 

 of the corpus juxta-restiforme. Nevertheless its ablation produces 

 contralateral motor symptoms, different from those after rootsection, 

 probable bound to proper afferent fibres 



On the other hand it is stated, that in the corpus geniculatum 

 mediale is the origin of direct centripetal fibres to the temporal 

 cortex cerebri, where hearing is localisated, and therefore it is 

 evident, that among the fibres in the lateral fillet must be sought 

 those, whose function is to conduct true sensory or acustic impul- 

 ses to the cortex. 



As we have seen, this fillet system is chiefly a contra-lateral system. 



It however has a homo-lateral representation. After lesions in the 

 dorsal or ventral octavus-systern its degenerations prevail contra- 

 laterally, but are not missing homolaterally. The contrary was the 

 case in the octavo- motor system. Degenerations in it were prevailing 

 homolaterally but were not missing contra-laterally. 



Therefore, we may speak of a differentiation within the central 

 system between the chiefly homolateral octavo-motor system and the 

 chiefly contra-lateral sensory octavus-system. 



But it must be kept in mind, that this differentiation is not at 

 all a sharp one. Both systems are originating from the dorsal, the 

 intermediary and the ventral octavus-systems, and as we have seen , 

 in describing details, often those octavo-motor and sensory-octavus 

 systems are provided by the same fibres. 



For instance, MONAKOW'S fibres, true sensory-octavus fibres, send 

 fibres (collaterals) in the octavo-motor system through the fasciculus 

 praedorsalis , and on the contrary, from true octavo-motor tracts as 

 the ascending and descending DEITERS tracts are, transverse fibres 



