NELTKOGLIA. 



183 



NEURILEMMA. Surrounding the individual nerve fibres of a bun- 

 dle. 



The formula E. P. E. N., composed of the initial of the name of 

 the investments from without inward, will aid the memory. 



The epineurium serves to protect the organ in its passage, and to 

 support the nutrient blood-vessels and the channels of lymphatics. 

 The fibres run both longitudinally and transversely. The perineu- 

 rium, arranged in dense bands, forms distinct sheaths for the nerve 

 bundles, the fibres running, for the most part, circularly. The endo- 

 neurium not infrequently divides the nerve bundles into smaller or 

 primitive bundles. It supports the blood capillaries, contains small 

 lymph-spaces, and its nuclei are frequently large and prominent. 



The final distribution of the elements of a nerve trunk is effected 

 by subdivision; first, of the large, and afterward of the primitive 

 bundles or fasciculae. The perineurial sheaths are prolonged, fur- 

 nishing the dividing bundles, even to the final distribution, where, 

 .around terminal and single medullated fibres, the sheath remains as 

 a layer of exceedingly delicate flattened cells. The necessity for the 

 endoneurium ceases with the ultimate subdivision of the nerve fas- 

 ciculus. 



NEUROGLIA. 



The sustentacular or supporting tissue of the brain and spinal cord 

 differs materially from ordinary connective tissue. It presents an 



FIG. 120. NEUROGLTA, FROM BENEATH THE PIA MATER OF THE SPINAL CORD. 



A. Network of neuroglia fibrils. 



B. Spider (Deiter's) cells. 



C. Nerve fibres in T. S. 



X400. 



