SYMPATHETIC SYSTEM IN MAMMALS 239 



tips of the growing branches of the vagi into the walls of thecesopha- 

 gus. Furthermore, it is impossible to trace cells from any other 

 source. There is no evidence as yet of the migration of cells 

 from the sympathetic trunks or from the prevertebral plexuses 

 toward the walls of the digestive tube. Neither cellular nor 

 fibrous connections occur between the sympathetic trunks or the 

 prevertebral plexuses and the sympathetic plexuses in the walls 

 of the digestive tube 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 

 oesophagus except along the fibers of the growing branches. These 

 courses are still plainly visible. The migrant cells in the walls of 

 the oesophagus have become arranged in more definite rings, and 

 none are found scattered in the surrounding tissue. Numerous 

 cells still accompany the fibers of the vagi 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 prox- 

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

 those still remaining probably subserve a supporting function. 

 The more distal parts still contain numerous cells. It is probable, 

 however, that the migration of cells along the vagi does not con- 

 tinue far beyond this stage. In the region just anterior to the 

 stomach, the vagus trunks have broken up into a loose network 

 which is the beginning of the oesophageal plexus. Vagus fibers 

 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 no fibrous connections 

 as yet between them and the anlagen of the sympathetic plexuses 

 in the walls of the digestive tube. 



In embryos 16 mm. in length, the vagus trunks as well as their 

 branches, many of which have established connections with the 

 myenteric and the submucous plexuses, are apparently free from 

 migrating cells. In the walls of the oesophagus, the cells which 

 have wandered in are aggregated into more or less distinct groups 

 arranged in two broken rings. The myenteric and the submu- 

 cous plexuses are thus becoming distinct. A similar arrangement, 

 though less definite, is apparent also in the walls of the intestine. 



