58 ATLAS OF NERVE CELLS 



Plate XXIX. shows a group of cells of smaller size than those already shown and chiefly 

 triangular in shape, which is found on the median border of the thalamus in its posterior 

 portions. These cells are not only grouped together, but are scattered along the median 

 surface of the thalamus in a thin layer over a considerable area. The large group is the 

 ganglion habenulae, shown as a distant hillock (/t) in Fig. 9, A. This ganglion gives rise to 

 a set of fibres which pass backward to the level of the posterior commissure, forming the pillars 

 of the pineal gland. It also gives origin to a band of fibres which passes downward and 

 backward between the red nuclei of the tegmentum to a small mass of gray matter lying 

 between the crura. This band is the fasciculus retroflexus of Meynert. It is shown in Fig. 8. 



The majority of the cells of the ganglion are triangular, with three chief dendritic branches, 

 but some are polygonal, with many dendrites. The neuraxon is very fine, and has few, if 

 any, collaterals. The majority of the neuraxons turn downward and probably pass into the 

 fasciculus retroflexus. In the plate the free median border of the thalamus is seen to the left. 



