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HOVEY JORDAN 



ing membrane. The middle portion of the "cell body is spindle 

 shaped and its superficial end is prolonged, as has been stated, 

 into a process which reaches to the lumen of the brain. This 

 process is differentiated into an outer, less refractive portion, the 

 sheath, and a very fine, highly refractive axial fibril (fbrl.'). It 

 is this fibril which projects into the lumen and contributes to the 



Fig. B. Parasagittal section, to show ependymal cells of the sub-commissural 

 organ and the connections of their fibrils. (Compare with figure 3.) 100 days. 

 X 750. 



formation of Reissner's fiber. Its deep end can be traced as far 

 as the nucleus of the cell, but, so far as I can discern, not beyond 

 the nucleus (figs. B and 5). 



It is to be seen in sagittal sections, where Reissner's fiber can 

 be traced throughout the entire length of the spinal cord, that it 

 extends continuously from its origin in the brain to its insertion 



