148 



NEEVOUS TISSUES 



FIG. 163. DIAGRAM OF THE ORIGIN AND RELATIONS 

 OF THE PERIPHERAL MOTOR AND SENSORY NEU- 

 RONS. 



A cylindrical section of the spinal cord, with its 

 ventral and dorsal nerve roots, is shown, a, nerve 

 cell of the ventral horn whose axon passes through 

 the ventral nerve root, 6, to its peripheral termina- 

 tion, c; at d is a unipolar sensory nerve cell in the 

 dorsal root ganglion; its process immediately divides 

 into a peripheral and a central branch. The central 

 branch enters the spinal cord and at e divides into 

 an ascending, /, and a descending, g, branch from 

 both of which numerous collaterals, h, enter the gray 

 matter and terminate in fine end brushes. The 

 peripheral branch of the spinal ganglion cell enters 

 a spinal nerve and finds its way to its termination 

 which is here represented in the skin; it terminates 

 partly by free endings among the epithelial cells, i, 

 and partly in connection with a sensory end organ, 

 k, in this case a tactile corpuscle of Meissner. (After 

 von Lenhosse'k.) 



trate the meninges these 

 lymphatic vessels are said 

 to be continuous with the 

 similar vessels of the- 

 dura mater. 



Minute nerve fiber 

 bundles, nervi nervorum, 

 are also found in the epi- 

 neurium; their fibers are 

 mostly, if not entirely, 

 distributed to the blood- 

 vessels. 



GANGLIA 



A ganglion may be 

 described as a group of 

 nerve cells occurring in 

 the course of a peripheral 

 nerve trunk. The larg- 

 est of the ganglia form 

 fusiform swellings in the 

 course of the nerve, which 

 are visible to the naked 

 eye. The smallest, on 

 the other hand, contain 

 not more than half a 

 dozen nerve cells, and 

 these must be sought with 

 the aid of the micro- 

 scope and can only be 

 found by the most care- 

 ful observation. 



Whatever may be their 

 size, all ganglia appear 

 to have a similar struc- 

 ture, except for those 

 differences which charac- 

 terize the sympathetic as 



