246 ALBERT KUNTZ 



from the sympathetic trunks represent later connections, and 

 play only a secondary part in their development. 



These conclusions differ widely from the views hitherto gener- 

 ally accepted concerning the development of the cardiac plexus 

 and the sympathetic plexuses in the walls of the visceral organs, 

 but the facts on which they are based are perfectly clear. Fur- 

 thermore, they obviate certain difficulties which arise in any 

 attempt to derive these plexuses from the sympathetic trunks. 

 The anlagen of the sympathetic plexuses in the walls of the vis- 

 ceral organs are present before any traces of the prevertebral 

 plexuses or of cells migrating peripherally from the sympathetic 

 trunks are found. It is obvious, therefore, that the vagal sym- 

 pathetic plexuses cannot be derived from the sympathetic trunks. 

 These findings also give the vagi an importance in the develop- 

 ment of the sympathetic nervous system which has hitherto been 

 unrecognized, but which is in complete harmony with other known 

 facts. 



V. DISCUSSION OF RESULTS, AND CONCLUSIONS 



(a) Migration of medullary cells. — Neurological literature con- 

 tains frequent allusions to the migration of medullary cells ever 

 since the time of Balfour (75). That pioneer among the inves- 

 tigators of the histogenesis of nerve-forming elements observed 

 cells which he believed to be nervous elements, migrating from 

 the embryonic neural tube in elasmobranchs. These observa- 

 tions were substantiated by Beard ('88) and Dohrn ('88, '91). 

 Herrick ('93) observed medullary elements migrating from the 

 motor niduli into the ventral roots of the spinal nerves in amphib- 

 ians, reptiles, and mammals. Ganglion cells have also been found 

 occasionally in the motor nerve-roots in adult animals. Such 

 cells were observed by Freud (78) in the ventral roots of the spinal 

 nerves in Petromyzon, and by Schafer ('81) and Kolliker ('94) 

 in the ventral roots of the spinal nerves in the cat. Thompson 

 ('87) described cells which he interpreted as degenerating gan- 

 glion cells, in the third and fourth cranial nerves in man. 



More recent investigators have frequently observed migrant 



