SYMPATHETIC NERVOUS SYSTEM IN MAN 175 



For the purposes of the present paper it will suffice to set forth 

 the views which were prevalent at that time and to consider 

 somewhat more fully the several papers which have appeared 

 during the past decade. 



While the great majorit}^ of the investigators in this field have 

 agreed that the sympathetic is derived from the cerebrospinal 

 nervous system, a few, of whom Camus ('12) is the most recent, 

 have attributed to this division of the nervous system a meso- 

 dermal origin. Inasmuch as no^ purpose can be served at this 

 time by discussing a theory which is so obviously erroneous, the 

 work of the latter authors will not be considered further in this 

 paper. 



There has always been a divergence of opinion among the ad- 

 vocates of the ectodermal origin of the sympathetic nervous 

 system regarding the exact sources and the histogenesis of the 

 sjanpathetic cells. Ever since the genetic relationship of the 

 sympathetic to the cerebrospinal nervous system was clearly 

 pointed out by Balfour ('77), the majority of the investigators 

 derived the cells which give rise to the primordia of the entire 

 sympathetic nervous system from the cerebrospinal ganglia or 

 the neural crest; however, there has been no general agreement 

 regarding the method by which these cells are displaced from 

 the cerebrospinal ganglia into the sympathetic primordia. Ac- 

 cording to the theory first set forth by Onodi ('86), cells are 

 forced to advance peripherall}^ from the distal ends of the spinal 

 ganglia by the pressure which is exerted by the newly formed 

 elements back of them. These cells become displaced toward 

 the dorsolateral aspects of the aorta and give rise to the primor- 

 dia of the sympathetic trunks. His, Jr. ('91), introduced the 

 principle of the active migration of the cells which give rise to 

 the sympathetic primordia along the paths of the spinal nerves 

 and the communicating rami. Some of the more recent investi- 

 gators are of the opinion that migration of cells from the spinal 

 ganglia occurs earlier than was observed by His, Jr., and that 

 the majority of the cells which enter the primordia of the sympa- 

 thetic trunks migrate through the mesenchymal tissue or in 

 advance of the growing fibers of the spinal nerves and the com- 



