NERVOUS TISSUE 



147 



have been found between ganglion cells in the retina by Dogiel, and slender nerve 

 fibers appear to anastomose in tissue cultures; but the staining of individual cells 

 by the Golgi method, and the way in which degeneration may be limited to cell 

 territories, are regarded as strong evidence against the existence of a general syncytium. 



STRUCTURE OF GANGLIA. 



Although a ganglion is characterized by the accumulation of the bodies 

 of nerve cells, it is traversed by many fibers, as seen in the section of a 

 spinal ganglion (Fig. 133). Under higher magnification the cell bodies 

 appear as in Fig. 134. The nuclei are large vesicular structures, round 

 or oval in outline, containing a characteristic prominent nucleolus. They 

 are surrounded by abundant, darkly staining, finely granular proto- 



Blood vessel. 



Fat. Ganglion cells. 



Nerve fibers. 



Perineurium. 



root 

 of a spinal nerve. 



Center 



of the 



spinal 



ganglion. 



FIG. 133. LONGITUDINAL SECTION THROUGH A SPINAL GANGLION OF A CAT. X 18. 



plasm, which exhibits its fibrillar structure only with special methods. 

 Frequently the protoplasm contains pigment granules. The "reticular 

 apparatus" is said to be present always, and slender intracellular canals 

 (trophospongium) have been described (Figs. 5 and 6, p. 4). Fine- 

 meshed reticular networks have been found covering the exterior of the 

 nerve cells, and they have been ascribed both to the terminal ramification 

 of nerve fibers and to branches of the supporting tissue. A ganglion cell 

 is often surrounded by flat or stellate cells arranged in concentric layers 

 so as to form a sheath. Within the sheath there is a homogeneous mem- 

 brane or capsule, on the inner side of which are cells arranged in a single 

 layer, corresponding to the cells within the neurolemma of peripheral 



