154 C. WINKLEK. THE CENTEAL COURSE 



From the nucleus parvocellularis a great number of fibres are 

 issuing. They leave its hilus and enter in the important systema 

 dorsale. After removal of the labyrinth these fibres degenerate 

 contra-laterally and in that case the contro-lateral nucleus, especially 

 its hilus , is degenerated nearly as intensely as the lateral surroun- 

 dings of the homolateral nucleus. 



Pigeons therefore, having no ventral octavus-system , receive by 

 means of the systema dorsale nervi octavi rootfibres to both nuclei 

 parvocellulares. 



Each nucleus parvocellularis, a very important nucleus of the 

 FI1P 1 nerves receive a bilateral innervation of rootfibres from 

 the n. octavus. 



The rabbit has not such a bilateral distribution of rootfibres 

 towards the dorsal nucleus or towards any other of the octavos-nuclei. 



After one-sided removal of the labyrinth in rabbits also fibres are 

 found passing through the dorsal part of the raphe , but they only 

 reach the nucleus of the VI th nerve. 



The important bundle of root-fibres to the contralateral nucleus 

 parvocellularis however is proper to pigeons. In rabbits it is mis- 

 sing. And this is a fact of physiological interest. 



Now the dorsal system is not exclusively formed by this bundle. 

 A great many transverse dorsal fibres enter from the portio interna, 

 and increase the quantity of rootfibres in the dorsal systema. 



These fibres offer again many points of comparison with those 

 in rabbits. 



Rootfibres in both animals are going to the homolateral nucleus 

 of the VI th , in both fasc. longitudinales posteriores, and to the 

 contra-lateral VI th nerve. 



In pigeons however the direct innervation of the homolateral 

 VI th nucleus is a slight one , and the innervation of the contra-lateral 

 VI th nucleus through the fasciculus long, posterior is also slight, 

 as the greater number of rootfibres, found here in the contra- 

 lateral fasciculus longitudinalis posterior, retires towards the contra- 

 lateral nucleus parvo-cellularis. 



In this way, only a few rootfibres enter in both VI th nuclei. 



At different levels however rootfibres enter again in both fasciculi 

 longitudinales posteriores, going to both nuclei of the IV th and of 

 the III th nerve. Only a few fibres are reaching those nuclei. 

 Therefore in pigeons all motor nuclei of the eye on both sides are 

 only to a slight degree provided with octavus-rootfibres. 



In rabbits there is a notable quantitative difference as regards 

 the innervation of the motor nuclei of the eye. As described there, 



