75 



be particalarly adaptei to the supportinf? of the nerv^oas mech- 

 anisms peculiar to these regions. 



0. The Ependyma. — Tne epeniyna of the cerebellim presents 

 the usual palisaia of closely crowded cells forming the membra- 

 na limitans interna (Fig. 13). The cell-body is irregularly 

 pyramidal in form, the sides rarely tapering evenly to the 

 apex but exhibiting more or less bold cur/atures of outline. 



From the apex of the cell-body, a process, the ependymal 

 fibre, arises, and this pursues a course through the struct- 

 ures of the granular layer to near the outer limit of that 

 zone. I have not found a single instance where one of these 

 fibres passel beyond the granular into the molecular layer, 

 a fact of some possible phylogenetic value, indicating the 

 more ancient character of the internal region. 



The ependyma-f ibre is relatively stout, but its diameter 

 is far from uniform. There are fibres which have portions of 

 the length four or five times the thickness of the intervening 

 parts; see Pig. 18, b. Occasionally, knobs and other rounded 

 thickenings are found, particalarly at angles 'where the course 

 of the fibre changes abruptly. The trenJ of the fibre is never 

 conspicuously irregular, only such slight turns and windings 

 occurring as might be expected where obstructions are present 

 during the period of growth. The general trend is directly 

 towarl the surface of the cerebellar fold, the several fibres 

 lying more or less nearly parallel with each other. 



