Turner, MorpJiology of the Aviaii Brain. zGc^ 



to be considered a distinct nidulus. In the medulla of the 

 young dove ( Cohimba livia) and in a few other cases this 

 cell cluster appears to be undoubtedly distinct from the 

 lateral motor nidulus of the trigeminus, while in other cases 

 (some of the Turdidcr), it is evidently amalgamated with 

 that nidulus. Histologically, it could hardly be considered a 

 distinct nidulus. For, although the cells are not typical 

 pyramidal cells, and although they appear to differ from the 

 typical cells of the lateral motor nidulus of the trigeminal 

 nerve, neither are they typical fusiform or flask cells. Al- 

 though tending towards the flask cells in outline, yet they 

 agree with the pyramidal cells in the structure of their nuclei. 

 In haematoxylin and in aluminium-sulphate cochineal prepa- 

 rations, these nuclei are densely stained. After due consid- 

 eration it has been thought best to consider this cell cluster 

 as a slightly modified portion of the lateral motor nidulus 

 of the trigeminus, which portion occasionally becomes 

 distinct. 



Lateral Sensory Nidulus of the Fifth Nerve (Plate XVIII, 

 Fig. 8). — This nidulus lies near the lateral surface of the 

 metencephalon, and on the same level as the lateral motor 

 nidulus of the trigeminus. It lies about as near to the lateral 

 surface of the medulla as does the latter nidulus, but it lies 

 upon the opposite side of the deep inotor fasciculus of the 

 trigeminal nerve. The form of this nidulus is not constant 

 throughout the class Aves. In some cases [Hylocichla 

 Swainsoni) the outline of this nidulus is sub-spherical, while 

 in others ( Coluniba livia) it is somewhat irregular. This 

 nidulus is smaller than the lateral motor nidulus of the same 

 nerve. 



The cells of this nidulus are flask shaped. In haematoxy- 

 lin and in aluminium-sulphate cochineal preparations, these 

 cells are densely stained, and each one presents a faintly 

 stained nucleus and a densely stained nucleolus. The niduli 

 of these cells are relatively smaller than the niduli of sensory 

 cells usually are. These cells are loosely and irregularly 



