Turner, Alorpholog'y of the Avian Brain. 373 



above nidulus and between the surface and that tract of the 

 auditory nerve w^hich passes to the raphe, there is an incon- 

 spicuous nidulus. This nidulus contains a fevv^ scattered 

 fusiform cells and numerous Deiter's corpuscles. In hcema- 

 toxylin and in aluminium-sulphate cochineale preparations, 

 these cells are obscurely stained, and each one presents a 

 faintly stained nucleus, within which is a densely stained 

 nucleolus. 



Root Ganglion of the Auditory Nerve (Plate XVIII, Figs. 

 I, 4). — Within the skull cavity the avian eighth nerve bears 

 a small root ganglion. This ganglion is closely appressed 

 upon the metencephalon. Indeed, in some cases it is so inti- 

 mately connected with the brain that it resembles a super- 

 ficial nidulus. This ganglion contains large spindle-shaped 

 cells, which apparently are of the same type as those in the 

 Gasserion genglion. In hsematoxylin and in aluminium-sul- 

 phate cochineal preparations, these cells are densely stained, 

 and each cell presents a faintly stained spherical nucleus, 

 within which is a densely stained nucleolus. Unfortunately, 

 in all my sections that show this ganglion these cells are cut 

 approximately at right angles, thus rendering it impossible 

 to demonstrate whether or not each extremity of the cell is 

 prolonged into a nerve fibre. HoweveR, each cell is sur- 

 rounded by a nuclei-bearing sheath, which resembles the 

 sheaths described and figured for the cells of Gasser's gan- 

 glion (Plate XVIII, Fig. i). 



Nidulus of the Glosso-pharyngeal Nerve (Plate XVIII, 

 Fig. 16). — At the surface it is almost impossible to distin- 

 guish beteen the roots of the glosso-pharyngeal and pneumo- 

 gastric nerve, but when we pass entad a knowledge of the 

 physiological functions of each nerve renders the separation 

 of the glosso-pharyngeal and pneumogastric niduli an easy 

 matter. Both niduli lie at the meson and in the floor of the 

 fourth ventricle. But the nidulus of the glosso-pharyngeal 

 nerve lies further cephalad and extends forther dorsad than 

 the nidulus of the pneumogastric nerve. 



