390 John F. Holm 



the frontal part, which leaves quite at the ventral surface. The 

 two motor nuclei and the way in which the nerve leaves the brain 

 make it probable that the Facialis represents two metameric nerves 

 which have become united. 



Sanders (41) has evidently not studied the most ventral sections 

 or else the staining method he used has been unsuitable for the 

 object, as in horizontal sections stained with Iron-haematoxylin it 

 is very easy to follow the axis-cylinder processes of the large-celled 

 nucleus into the nerve. 



The Eighth Nerve or Acusticus. 



Sanders (41) describes the Acusticus as having two roots, one 

 dorsal, identical with the Radix dorsalis of the Ramus anterior 

 (which I will describe farther on) and one ventral which does not 

 exist. It is perfectly true that a few fibres besides the roots I have 

 already described leave the ganglion here and there and enter the 

 Medulla, also that it is sometimes the case that a few may be 

 derived from the ventral edge, but no big bundle enters the brain 

 from that quarter. The ventral root described by Sanders (41) is 

 probably nothing else than the lateral part of the Facialis root, 

 which on leaving the brain is pressed close to the Ganglion and in 

 transverse sections of objects where the continuation of the Facialis 

 has been lost through preparation it is easy to get figures which 

 suggest such a ventral root as Sanders describes. 



According to Ahlborn (2), the Acusticus has its origin in two 

 nuclei situated below the Facialis nucleus and their caudal end 

 should be on the level of the decussation of the Miillerian fibres. 



Haller (17), who has investigated the origin of the Acusticus 

 roots in Salmo, finds (as I have done in Myxine) that the region 

 from which this nerve springs is distributed over a large area, from 

 the most rostral part of the Oblongata down into the Vagus region 

 and chiefly through the exterior sensory region. 



He finds, contrary to previous suppositions, that the Acusticus 

 has both direct and indirect origin — i. e. — that it springs from 

 cells in the Medulla as well as from the cells in the Acustic 

 ganglion. 



I have found in a few instances, both with Golgi method and 

 in a preparation with Iron-haematoxylin, small sensory cells which 

 send their processes into the nerve. In Fig. 12, drawn from Golgi 



