THE SPINAL CORD AND CEREBELLUM loi 



fibres of the antero-lateral ascending tract, which are 

 derived either from the vesicular cylinder or from 

 cells adjacent to it.* 



The fibres of which the roots of spinal nerves are Fibres of 



the apmal 



composed are derived from many sources, but it is nerve- 



roots. 



possible to classify them, to some extent, according to 

 the parts which they supply and the nature of the 

 impulses they carry. When the fibres of the common 

 trunk are traced along their paths to the periphery, 

 some are found to end in muscle, some in sensory end 

 organs or sensory surfaces, and some in the sym- 

 pathetic ganglia. These latter constitute an important 

 chain stretching the whole length of the spinal cord 

 on either side. They are sometimes looked on almost 

 as a separate nervous system, but this view is only 

 justifiable in a limited extent. Like the parts which 

 they chiefly supply they are contained for the most 

 part in the body cavity, and acquire greater size and 

 importance in special regions. They have a double 

 connection with the spinal nerves, the one link being 

 the white ramus communicans, the other the gray 

 ramus communicans, which sends a recurrent branch 

 to the bloodvessels of the limbs.! These ganglia are 

 connected with the viscera of the body, and as these 

 are composed chiefly of muscular tissue, of sensory or 

 chemico-sensory surfaces or membranes with their 

 glands, and of bloodvessels, it seems natural to 

 suppose that the functions of the fibres passing 

 through the ganglia will be motor to the muscular 

 * Foster, loc. cit., p. 971. f Ibid., p. 171. 



