152 



IIA::I>-BOOK OF PHYSIOLOGY. 



FIG. 348. 



roots of their nerves. The 

 spinal cord, indeed, appears 

 to be a large source of the 

 fibres of the sympathetic 

 nerve. 



Through the communi- 

 cating branches between 

 the spinal nerves a"d the 

 prse-vertebral sympathetic 

 ganglia, which have been 

 generally called roots or 

 origins of the sympathetic 

 nerve, an interchange is 

 effected between all the 

 spinal nerves and the sym- 

 pathetic trunks; all the gan- 

 glia, also, which are seated 

 on the cerebral nerves, 

 have roots (as they are 

 called) through which fila- 

 ments of the cerebral nerves 

 are added to their own. So 

 that, probably, all sympa- 

 thetic nerves contain some 

 intermingled cerebral or 

 spinal nerve-fibres; and all 

 cerebral and spinal nerves, 

 some filaments derived 

 from the sympathetic sys- 

 tem or from ganglia. But 

 the proportions in which 

 these filaments are mingled 

 are not uniform. The 

 nerves which arise from the 

 brain and spinal cord retain 

 throughout their course 

 and distribution a prepon- 

 derance of cerelro-spinal 

 fibres, while the nerves im- 

 mediately arising from the 

 so-called sympathetic gan- 

 glia probably contain a ma- 

 jority of sympathetic fibres. 

 But inasmuch as there is 



