THE SPINAL CORD 85 



MICROSCOPIC ANATOMY 



Neuroglia. Occupying the interstices among the true nervous elements of 

 the central nervous system is a peculiar supporting tissue, the neuroglia, which 

 is of ectodermal origin. In the chapter on Histogenesis we learned that from 

 the original epithelium of the neural tube there are differentiated spongioblasts 

 and neuroblasts, as well as a special epithelial lining for the tube, the ependyma. 



Fig. 61. Ependyma and neuroglia in the region of the central canal of a child's spinal cord: 

 A, Ependymal cells; B and D, spider cells in the white and gray matter, respectively; C, mossy 

 cells. Golgi method. (Cajal.) 



The latter consists of long nucleated columnar cells which line the central canal 

 of the spinal cord as well as the ventricles of the brain (Fig. 61). In fetal life 

 their free ends bear cilia, which project into the lumen of the tube, and fine 

 processes from the outer ends extend to the periphery of the cord. In the adult 

 there are no cilia and the peripheral processes reach the surface only along the 

 posterior median septum and in the anterior median fissure. 



