SYMPATHETIC NERVOUS SYSTEM IN MAN 187 



cell-masses are very conspicuous all along the abdominal aorta, 

 (figs. 16 and 17, pv). At this stage some cells have already 

 become displaced laterally from these masses toward the pri- 

 mordia of the adrenal glands and along the renal arteries. The 

 greatest accumulation of sympathetic cells ventral to the abdom- 

 inal aorta occurs about the coeliac artery. The several plexuses 

 which arise along the abdominal aorta are not yet clearly de- 

 limited. Neither can fibers be traced from these plexuses into 

 the mesentery. As development advances these several plexuses 

 become more clearly differentiated, while the ganglionic masses 

 become relatively larger and more compact. From these gan- 

 glionic masses cells may be traced into the adrenal glands as well 

 as along the renal and spermatic (or ovarian) arteries. 



VAGAL SYMPATHETIC PLEXUSES 



The writer has presented evidence in the series of earlier papers 

 referred to above which shows clearly that throughout the entire 

 vertebrate series the pulmonary, the cardiac, and the enteric 

 plexuses, except in the aboral portions of the digestive tube, are 

 not genetically related to the sympathetic trunks, but arise from 

 cells of cerebrospinal origin which advance peripherally along the 

 paths of the vagus nerves. These findings were first substanti- 

 ated by Abel ('12) in embryos of the chick. Abel ('10) had pre- 

 viously derived the enteric plexuses in the chick exclusively from 

 cells which migrate ''from the spinal cord and the intervertebral 

 ganglia." Following the publication of the writer's earlier pa- 

 pers, she undertook a reinvestigation of the development of the 

 sympathetic nervous system in the chick. In this work she em- 

 ployed specialized methods and studied the development of the 

 sympathetic plexuses related to the vagi in considerable detail. 

 Her findings regarding the dvelopment of the pulmonary, the 

 cardiac, and the enteric plexuses agree in all essential respects 

 with the results of the work of the present writer which had 

 previously been published. Recently Stewart ('20) has pre- 

 sented evidence based on embryos of the rat which he interprets 

 as indicating ''that part if not all of the nerve cells found in the 



