SYMPATHETIC SYSTEM IN MAMMALS 237 



Later writers have generally assumed that the cardiac plexus 

 and the sympathetic plexuses in the walls of the visceral organs 

 have their origin in the sympathetic trunks, but the course of their 

 development has not been made clear. The literature bearing 

 on this point is conspicuously meager. 



My own observations, as indicated in a recent paper, 2 have 

 shown that the cardiac plexus and the sympathetic plexuses in 

 the walls of the visceral organs do not owe their origin to the sym- 

 pathetic trunks as has hitherto been supposed, but that the}- arise 

 from cells which migrate from the vagus ganglia and the walls of 

 the hind-brain along the fibers of the vagi. 



Because the origin of these plexuses is distinct and -eparate from 

 the origin of the sympathetic trunks and the sympathetic plex- 

 uses described above as prevertebral plexuses, they cannot prop- 

 erly be characterized as prevertebral sympathetic plexuses. 

 In view of their relation to the vagi I have chosen to designate 

 them as vagal sympathetic plexuses. The term "vagal sympa- 

 thetic" is a departure from the established nomenclature, but 

 inasmuch as there is no good collective term which could be ap- 

 plied to the cardiac plexus and the sympathetic plexuses in the 

 walls of the visceral organs, it has seemed well, for the sake of 

 clearness, to employ a new term. 



(b) Myenteric and submucous plexuses. — In transverse sections 

 of embryos 6 and 7 mm. in length, in the region of the cesophagus, 

 the vagus trunks appear as large bundles of loosely aggregated 

 fibers accompanied by numerous rounded or elongated cells. 

 These cells, which, as will be shown later, are of medullary and 

 ganglionic origin, are easily distinguished from the cells of the 

 surrounding mesenchyme by their larger size and the character- 

 istic chromatin structure of their nuclei. Many of them appear 

 to become separated from the nerve-trunks and to wander into 

 the walls of theoesophagus until the latter is completely surrounded 

 by these migrant cells. In a few sections short fibers are seen to 

 bend from the vagus trunks toward the cesophagus (fig. 13, vag. 



2 The role of the vagi in the development of the sympathetic nervous system. 

 Anatomischer Anzeiger, Bd. 35. no. 15. 16. pp. 381-390. 



