ORIGIN OF THE CEREBRAL NERVES. 499 



they constitute a part of the same formation as the anterior 

 nucleus. 



In regard to the medullary masses connected with these 

 nuclei it now becomes requisite to determine which of these 

 last are to be regarded as centres of origin, and which as 

 terminal masses, since they descend to them from, masses that 

 are still to be regarded as central. 



In the first place, the auditory nerve offers no parallel on 

 morphological grounds to the nearly allied and important 

 sensorial regions of the olfactory lobes and the optic nerve. For 

 no connecting arches pass from the pons for the formation of 

 the labyrinth, or rathsr the organ of Corti, which can be con- 

 sidered as the morphological homologues of those which pass 

 from the cortex of the cerebrum to the olfactory lobes and the 

 retina. 



While the medulla of the olfactory lobe and that of the 

 retina (as the optic nerve) run with converging fibres pre- 

 senting characters precisely similar to those of the upper link 

 of the projection system into the same terminal ganglion as 

 the white fibres coming from the cortex of the cerebrum, the 

 auditory nerve does not extend to any of these ganglia, but 

 enters into the grey matter of the central cavities, which is not 

 immediately connected with the central lobes. Its immediate 

 entrance into this structure,. as well as its form, makes the audi- 

 tory nerve analogous to the nerve roots, or to the inferior link 

 of the projection system. It is not however justifiable on this 

 account to associate the auditory nerve completely in the 

 further details of its course with the other nerve roots of the 

 peduncle of the cerebrum, and indirectly with the type of the 

 spinal cord. Deiters attempted to do this when he explained 

 both as members belonging to its lateral mixed system, the 

 other formations of which are represented by the glossopha- 

 ryngeal pneumogastric and accessory nerves, which are in the 

 same manner neither purely sensory nor purely motor. In 

 adopting this view, he only rehabilitated the old statements of 

 Galen, Fallopius, and Haller, according to whom the auditory 

 nerve, as the portio mollis formed a common nerve root with 

 the facial nerve. 



Deiters assigned this position to the auditory nerve in 



K K 2 



