OF THE NERVUS OCTAVUS. 155 



both nuclei of the VI th nerve are provided with a great many 

 rootfibres. There also the intensity of the innervation is nearly the 

 same on both sides. 



But besides the less important innervation of the IV th homolateral 

 nucleus through the fasciculus longitudinal posterior, there exists 

 the important homolateral ascendant DEITERS tract, carrying rootfibres 

 to the IV th and III th nuclei. 



Therefore in rabbits is found an intense innervation of both 

 nuclei N. VI, and a preponderant homolateral innervation of the 

 IV th nucleus and the distal end of the III th nucleus. 



This again is a difference of physiological interest. In pigeons 

 rootfibres of the VIII th nerve, go to all motor eye-nuclei. They are 

 few in number, bilateral in their paths, and nearly equal in number 

 on both sides. 



In rabbits rootfibres of the VIII th nerve also supply them. Many 

 of them provide both VI th nuclei, but the homolateral IV th and 

 III th nuclei are supplied by a much larger number of them than 

 the contralateral. 



As to the descendent rootfibres, the difference is less considerable. 

 In rabbits as in pigeons there are found prepondering rootfibres 

 in the homolateral fasciculus anterior of the cord, and in both it 

 is doubtful whether there are found rootfibres in the descending 

 tract of DEITERS in the lateral column. 



Their path has been exactly described. The chief results there- 

 fore of the investigation of the rootfibres in pigeons are. 



Pigeons have no ventral sy sterna N. octavi. Their dorsal sy sterna 

 is very important. The angular , the parvocellular and the magno- 

 cellular nuclei are intercalated in it as the tuberculum acusticum, the 

 dorsal nucleus N. VIII and the nucleus of DEITERS are in mammalia. 



The former two receive the endings of rootfibres. Not the magno- 

 cellular nucleus. 



Through the dorsal system the rootfibres of one N. octavus provide 

 both nuclei parvo-cellulares. 



Through the dorsal system the motor eye-nuclei receive a bilateral, 

 symmetrical, but a very slight innervation of octavus-root fibres. 



Through the dorsal system the fiomolateral motor horn of the 

 spinal cord at least in its cervical part - - receives a not un- 

 important innervation of root-fibres. 



