383 



The cells surrounding the oesophagus are not yet arranged in well 

 defined rings but are loosely scattered in the tissues (Fig. 1 me.). 



The fibers of the vagus nerves do not yet extend beyond the 

 region of the heart. In sections through the stomach the paths of 

 the vagus branches are indicated by the presence of numerous cells 

 like those described above. These cells show a tendency to spread 

 in the walls of the stomach until they have completely surrounded it. 

 Similar cells are found scattered in the walls of the intestine as far 

 as the latter can be traced. Thus it appears that having once become 

 established in the anterior regions of the digestine tube, these cells 

 migrate posteriorly along its course. 



That these migrant cells found in the walls of the intestine have 

 wandered out from the vagus trunks can not be doubted. It is im- 

 possible to trace them to any other source. There is no evidence of 

 the migration of cells ventrally from the ganglia of the sympathetic 

 trunks either in the region of the oesophagus or in the mesentery. 

 A. few cells can be traced ventrally from the sympathetic trunks to 

 the ventral level of the aorta in the regions in which later the coeliac 

 and hypogastric plexuses arise, but none can be traced beyond these 

 points. Neither cellular nor fibrous connections are established between 

 the ganglia of the sympathetic trunks and the myenteric and sub- 

 mucous plexuses until the latter have become well established. 



In transverse sections of embryos 9 mm in length there is no 

 evidence of cells wandering from the vagus trunks toward the walls 

 of the oesophagus except along the fibers of the growing branches. 

 These courses are still plainly visible. The migrant cells have become 

 arranged in more definite rings around the oesophagus, and none are 

 found scattered in the surrounding tissues. Numerous cells still ac- 

 company the fibers all along their course and seem to escape freely at 

 their growing tips. 



In embryos 12 mm in length the number of cells in the proximal 

 part of the vagus trunks has materially decreased. Most of the cells 

 still remaining probably serve a supporting function. The more distal 

 parts still contain numerous cells. It is probable, however, that 

 migration of cells along the vagus trunks does not continue far 

 beyond this stage. In the region anterior to the stomach the vagus 

 trunks have broken up into a loose network surrounding the oesophagus. 

 This is obviously the beginning of the oesophageal plexus. Vagus 

 fibers which are still accompanied by numerous cells may now be 

 traced along the lesser curvature of the stomach. The anlagen of the 

 coeliac plexus are well established, but there are still no fibrous con- 



