110 HISTOLOGY. 



individual nerve cells, following their branches to their smallest subdivisions, 

 whereas similar adjoining cells are entirely unaffected. This extraordinary 

 method is of the greatest value, but it is capricious and the silhouettes 

 produced are in part coarse and artificial appearances. 



The ganglia are surrounded by connective tissue sheaths, continuous 

 with the perineurium, which send prolongations into their interior to 

 invest the cell bodies and fibers. They contain an abundance of blood 

 vessels so that a cell body may be surrounded with capillaries. The spinal 

 and sympathetic ganglia will be described in turn. 



S phial ganglia are found on the dorsal roots of spinal nerves; similar 



Cross section of medullated nerve fibers. 



Nucleated sheath. 

 Protoplasm. 





Longitudinal view 



of medullated 



nerve fibers. Surface view of 



nucleated sheath. 



FIG. 134. FROM A CROPS SECTION OP THE SEMILUNAR GANGLION- OF MAN. X 240- 



The cell processes cannot be seen. At x the protoplasm of the ganglion cell has retracted and simulates 



a process. In the axis of the transversely cut nerve fibers the axis cylinders are seen in section. 



structures occur on the dorsal roots of the cerebral nerves. The general 

 relations of the cell bodies and fibers are shown in Fig. 133, a longitudinal 

 section through the dorsal and ventral roots. Fig. 134, from the semilunar 

 [Gasserian] ganglion of the trigeminus, shows the component structures 

 on a large scale. In the upper part of the figure there are characteristic 

 nerve cells such as have the T-shaped process, the development of which 

 from bipolar cells has already been described. The processes are not 

 seen in the section. Each of these cell bodies is surrounded by a nucleated 

 capsule said to be continuous with the neurolemma of its fiber. Fig. 135 

 show r s one of these cell bodies containing canaliculi which have been 

 regarded as nutritive passages from the exterior, and as secretory or 



