PEEIPHEEAL-NERTE BOOTS, SPINAL GANGLIA, SPINAL COBD. 



343 



ends in a minute brush. The places from which pass ofE these "collaterals" 

 from the stem are usually marked by a slight enlargement. 



The spinal white matter is interwoven with numerous, radiating septa, 

 made up of neuroglia, and in them run the blood-vessels, coming from the 

 periphery of the cord. 



The nerve-fibers in the white matter are all surrounded by a loose net-work of 

 nevroglia-flhers. In tlie gray matter it is found most densely deposited near the 



Fig. 220. — Longitudinal section through the lateral column of a newborn 

 pup. On the left is shown, after an original preparation of RamOn y Cajal's, axis- 

 cylinders sending collaterals into the gray matter, and others, coming from cells 

 there situated, dividing into an ascending and a descending branch. The cellular 

 connections to the right are schematic. 



central canal, in the substantia grisea. After the Weigert stain, it appears to the 

 naked eye as a dark-blue spot. 



Less dense than this, but thicker than in the white matter, is the neuroglia- 

 mesh of the ventral horns. It is most sparse in the substantia gelatinosa Eolandi. 



The entire periphery of the cord is covered with a thin mantle of almost pure 



